Stooge, nevertheless last to protest (4)
I believe the answer is:
butt
'stooge' is the definition.
('butt' can be a synonym of 'stooge')
'nevertheless last to protest' is the wordplay.
'nevertheless' becomes 'but' (I've seen this before**).
'last to' suggests the final letters.
The final letter of 'protest' is 't'.
'but'+'t'='BUTT'
(Other definitions for butt that I've seen before include "Strike with head" , "Knock head" , "Contralto" , "Fag-end" , "Cigar end" .)