After meal fails to start, split punch (8)
I believe the answer is:
uppercut
'punch' is the definition.
(I've seen this before)
'after meal fails to start split' is the wordplay.
'after' is a charade indicator (letters next to each other).
'meal' becomes 'supper' (supper is a kind of meal).
'fails to start' means to remove the first letter.
'split' becomes 'cut' (synonyms).
'supper' with its first letter removed is 'upper'.
'upper' put next to 'cut' is 'UPPERCUT'.
(Other definitions for uppercut that I've seen before include "one must take it on the chin" , "Blow from fist to chin" , "Swinging blow directed at an opponent's chin" , "Part of boxer's repertoire" , "Boxer's blow" .)