Dismiss Sale's back, punching rugger thug (4,3)
I believe the answer is:
rule out
'dismiss' is the definition.
(I've seen this in another clue)
'sale's back punching rugger thug' is the wordplay.
'back' says to take the final letters.
'punching' is an insertion indicator (some letters punch a hole in others).
'rugger' becomes 'RU' (rugby union - rugger can mean rugby).
'thug' becomes 'lout'.
The final letter of 'sale' is 'e'.
'ru'+'lout'='rulout'
'e' inserted into 'rulout' is 'RULE OUT'.
(Other definitions for rule out that I've seen before include "Exclude as irrelevant or inadmissible" , "Exclude as a possibility" , "Exclude from consideration" , "'Eliminate from consideration (4,3)'" , "Dismiss from consideration" .)