Youngsters oddly shunned nudist clubs? (5,4)
I believe the answer is:
minor suit
'clubs?' is the definition.
(I've seen this before)
'youngsters oddly shunned nudist' is the wordplay.
'youngsters' becomes 'minors' ('minor' can be a synonym of 'youngster').
'oddly shunned' means one should take alternating letters (letters in odd-numbered positions removed).
The alternate letters of 'nudist' are 'uit'.
'minors'+'uit'='MINOR SUIT'
(Other definitions for minor suit that I've seen before include "clubs, for example" , "clubs, perhaps" , "(In bridge) clubs or diamonds" , "Clubs, say" .)