Excuse no one – bar should be raised (7)
I believe the answer is:
evasion
'excuse' is the definition.
(I've seen this before)
'no one bar should be raised' is the wordplay.
'one' becomes 'i' (Roman numeral).
'bar' becomes 'save' (both can mean 'except').
'should be raised' says the letters should be written in reverse (in a down clue, letters go up).
'no'+'i'+'save'='noisave'
'noisave' in reverse letter order is 'EVASION'.
(Other definitions for evasion that I've seen before include "A dodgy answer or excuse" , "Illegal avoidance (of tax)" , "Deceptive action" , "Fencing" , "Hedging" .)