Brought up rotten fish (3)
I believe the answer is:
dab
'fish' is the definition.
(I've seen this before)
'brought up rotten' is the wordplay.
'brought up' says the letters should be written backwards (down clues only).
'rotten' becomes 'bad' ('bad' can be similar in meaning to 'rotten').
'bad' written backwards gives 'DAB'.
(Other definitions for dab that I've seen before include "Fish; small amount" , "Bad sort of small fish" , "Expert; flat fish" , "Digital radio" , "Fingerprint - fish" .)