Cat unsuitable for part in play (3)
I believe the answer is:
act
'part in play' is the definition.
'act' can be an answer for 'play' (I've seen this in another clue). I am not sure about the 'part in' bit.
'cat unsuitable' is the wordplay.
'unsuitable' indicates an anagram (letters not in suitable order).
'cat' with letters rearranged gives 'ACT'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for act that I've seen before include "Perform - part of a play" , "Subdivision of a play" , "performing group" , "Exploit" , "Aussie parliamentarians exert influence here?" .)