Overlook objections to a counterfoil (4)
I believe the answer is:
stub
'a counterfoil' is the definition.
('stub' can be a synonym of 'counterfoil')
'overlook objections' is the wordplay.
'overlook' says the letters should be written in reverse (I've seen 'overlooked' mean this).
'objections' becomes 'buts' (as in 'no ifs, no buts').
'buts' written backwards gives 'STUB'.
'to' acts as a link.
(Other definitions for stub that I've seen before include "A short stump as of cigar" , "Pencil or cigarette end" , "Broken-off end" , "Strike against hard object - one's toe, perhaps" , "this pollution by smoker?" .)