PM's retreat (8)
I believe the answer is:
chequers
'pm's retreat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for chequers that I've seen before include "the PM's weekends?" , "Official country residence of the British Prime Minister" , "Major retreat in the past, for example" , "PM's retreat" , "British PM's official country residence" .)