Losing seat (6)
I believe the answer is:
behind
This clue is a double definition.
'losing' is the first definition.
(synonyms)
'seat' is the second definition.
(I know that seat can be written as behind)
(Other definitions for behind that I've seen before include "Taking place in secret" , "Rear - losing" , "Responsible for" , "Hidden by; late" , "Seat" .)