Constituency MP prefers (4,4)
I believe the answer is:
safe seat
'constituency mp prefers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for safe seat that I've seen before include "MP's desire" , "Politician's dream" , "Constituency unlikely to be lost" , "What the Uxbridge and South Ruislip constituency is for Boris" , "one of a great majority" .)