Before onset of unconsciousness, butt ruddy bore (7)
I believe the answer is:
endured
'bore' is the definition.
('endure' can be a synonym of 'bear')
'before onset of unconsciousness butt ruddy' is the wordplay.
'before' means one lot of letters go next to another.
'onset of' says to take the initial letters.
'butt' becomes 'end' (I've seen this before**).
'ruddy' becomes 'red' ('red' can be a synonym of 'ruddy').
The first letter of 'unconsciousness' is 'u'.
'u' after 'end' is 'endu'.
'endu'+'red'='ENDURED'
(Other definitions for endured that I've seen before include "Bore or tolerated" , "Withstood" , "Put up with something" , "Borne" , "Bore; put up with" .)