Sulk finishes in which you eff off (4)
I believe the answer is:
huff
'sulk' is the definition.
(I've seen this before)
'finishes in which you eff off' is the wordplay.
'finishes in' says to take the final letters (I've seen 'finish in' mean this).
The final letters of 'which you eff off' are 'HUFF'.
(Other definitions for huff that I've seen before include "Passing mood of anger" , "Fit of petulance - encountered playing draughts?" , "A state of annoyance" , "Fit of irritation" , "fit of anger" .)