Popular as might be spanking bottom, oh I say? Nudge, nudge, wink, wink! (8)
I believe the answer is:
innuendo
'wink' is the definition.
(thesaurus)
'popular as might be spanking bottom oh i say? nudge nudge wink' is the wordplay.
I cannot quite understand how this works, but
'popular' could be 'in' ('in' can mean trendy) and 'in' is located in the answer.
'be' could be 'end' (ending is a kind of being) and 'end' is found in the answer.
'oh' could be 'o' and 'o' is present in the answer.
The remaining letters 'nu' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for innuendo that I've seen before include "hint" , "Insinuation - suggestion" , "Disparaging suggestion" , "Disparaging oblique remark" , "suggested" .)