Mostly nasty about US city recordings (5)
I believe the answer is:
vinyl
'recordings' is the definition.
(vinyl records)
'mostly nasty about us city' is the wordplay.
I cannot really see how this works, but
'city' could be 'ny' (short for New York) and 'ny' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for vinyl that I've seen before include "LP-making material" , "PVC" , "& 24 Across Pre-CD disc" , "Synthetic plastic" , "LP material" .)