Part of sleeve is a hit (4)
I believe the answer is:
cuff
I believe this clue is a double definition.
'part of sleeve' is the first definition.
('cuff' is part of 'sleeve')
'a hit' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for cuff that I've seen before include "End part of sleeve" , "by one hand" , "Smack; end of shirt sleeve" , "Blow - on the wrist?" , "beat" .)