A trick in Who's Who, perhaps (4,3,4)
I believe the answer is:
find the lady
'a trick in who's who perhaps' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'a trick in who's who perhaps' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
'in' is found in the answer.
'perhaps' could be 'y' (I've seen this in other clues) and 'y' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for find the lady that I've seen before include "Three-card trick" , "Cherchez la femme" , "there's a trick to it" .)