Feeble, unable to finish hit (3)
I believe the answer is:
lam
'hit' is the definition.
(to 'lam' means to hit hard)
'feeble unable to finish' is the wordplay.
'feeble' becomes 'lame' (synonyms).
'unable to finish' means to remove the last letter.
'lame' with its last letter taken off is 'LAM'.
(Other definitions for lam that I've seen before include "Thrash; (US) escape" , "Escape, get away" , "Go on the - - , (US sl.)" , "Thump; leg it" , "On this, you're in flight, especially from the police" .)