Blubber smells revolting (3)
I believe the answer is:
sob
'blubber' is the definition.
(I've seen this before)
'smells revolting' is the wordplay.
'smells' becomes 'bos' (B.O. is an example).
'revolting' says the letters should be written backwards.
'bos' in reverse letter order is 'SOB'.
(Other definitions for sob that I've seen before include "Cry noisily" , "Wep convulsively" , "Snivel" , "Cry loudly" , "Weep convulsively" .)