Is it not for Judy to say? (9)
I believe the answer is:
punchline
'judy to say?' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'is it not' is the wordplay.
I cannot quite understand how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
'not' could be 'un' (prefix meaning 'not') and 'un' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'for' acts as a link.
Can you help me to learn more?
(Other definitions for punchline that I've seen before include "joke leading to row after church" , "Part of joke" , "This should make you laugh" , "one is expected to laugh at" , "Gag's ending" .)