Ordinary, large punches a mistake in scrap (7)
I believe the answer is:
abolish
'scrap' is the definition.
(I've seen this before)
'ordinary large punches a mistake' is the wordplay.
'ordinary' becomes 'O' (abbreviation e.g. O-Levels).
'large' becomes 'L' (eg in clothes sizes).
'punches' is an insertion indicator (some letters punch a hole in others).
'mistake' becomes 'bish' (informal term for an error).
'o'+'l'='ol'
'a'+'bish'='abish'
'ol' placed into 'abish' is 'ABOLISH'.
'in' acts as a link.
(Other definitions for abolish that I've seen before include "Put an end to (custom)" , "Put an end to, cancel" , "Quash" , "Stop or put an end to" , "ditch" .)