Rotten buffet, strange (7)
I believe the answer is:
offbeat
'strange' is the definition.
(I've seen this before)
'rotten buffet' is the wordplay.
'rotten' becomes 'off' (rotten food is 'off').
'buffet' becomes 'beat' (I've seen this before).
'off'+'beat'='OFFBEAT'
(Other definitions for offbeat that I've seen before include "Strange" , "Wacky; syncopated" , "Way-out" , "Wacky, eccentric" , "Strikingly unconventional" .)