Having checked further it seems that either clue could do. The answer relates to a type of disciple of Zeno and not, as I had thought, to a specifically-named one. That'll teach me to try and catch out Kate!!
I must admit I had similar thoughts about this clue but I was persuaded that in all probability (and I have no idea if I am right or wrong here) if it was a discipline it would have ended in 'ism'. I am so glad that I am not the only one to query that clue.