A classic synthesised clap sound is basically a noise-snare type of sound with multiple transients. In the case of a 909 clap you have a white noise burst with 4 transient peaks at the start roughly 10-12 milliseconds apart. I guess it uses a looping envelope to achieve this, and some synths, like the Andromeda A6 have a looping envelope allowing you to make this type of noise clap very easily.

It's that multiple transient that gives the clap effect of an electronic clap. Without that you have an electronic snare sound.

So the most basic way of doing it on the Pro5 would be to make a white noise burst, with the filter in a pleasing position, or perhaps closing with the filter envelope and to record the result. Make 4 recordings of the same sound and then using your sample or audio editor take the first 10-12 milliseconds from 3 of the recordings, fade each one out and stictch them together ending in the 4th unedited sound.
this will give you one clap. export/bounce that to make a new sample you can use in your compositions.

That's the most basic way and similar to what I did.

However what I did was more complex.
Firstly I synthesised my own noise, and this is the part that I really need my synth in front of me to remember exactly how but I think what I did was:

1) use OSCB as a modulator and turn mix 2 to off so it would not enter the audio path of the synth
2) set OSCB as square and turn the pulse very very narrow, right to the point that it cuts out
3) use the polymod section so add OSC B to OSC A, have OSC A set to any waveform (probably triangle) somewhere at around 2 O'clock you should hear OSC 1 turn to noise.

then it's a question of pitch (of OSC1 and OSC2), OSC2 FM amount and pulse width settings to generate a pleasing noise tone.
You can also use the filter self oscillating instead of OSC A, which Will give you more modulation options with the filter envelope and resonance amount.

Secondly, on top of that what I did was think about frequency bands and synthesised a different noise tone for each band eg, 2 sounds, one occupying the lows and another the highs. sometimes 3 sounds for lows, mids and highs. I then made multiple recordings and mixed the result with band-passed channels. Also I recorded each element of each band twice to give a true stereo result.

OK that's one way of doing it.

Another way of synthesising a clap on an analogue synth is to use pulse width to give a multiple transient.
You know that you can turn the pulse width on many synths so that that it is so thin (or even in a negative state) that it in effect mutes the square wave.
You can take advantage of that to make a double transient clap sound on synths that

a) allow FM of the Oscillator with white noise
b) allow modulation of the pulse width with an envelope.

Unfortunately the Pro5 doesn't allow (b) that but it does allow LFO to change the pulse width so you can use the first method to turn OSCA into a noise generator and have it set to pulse width and THEN modulate that pulse width with the LFO. that also works I think. So the rise (or fall) of the LFO will create a muted area at some point. use the mod wheel to set it so it only just mutes for a fraction of a second, you then have to time the key presses to coincide with this muted section... not what I did for that sample library for obvious reasons.

That's basically it. You may not be able to do it as I say exactly because I don't have the synth in front of me, some of the method here may be slightly off, but at least you'll have something here to think about and experiment with.