Liberal MP getting stuck into booze (5)
I believe the answer is:
ample
'liberal' is the definition.
(I've seen this in another clue)
'mp getting stuck into booze' is the wordplay.
'getting stuck into' is an insertion indicator.
'booze' becomes 'ale' (type of alcohol).
'mp' placed into 'ale' is 'AMPLE'.
(Other definitions for ample that I've seen before include "Large, accommodating" , "Spacious" , "Buxom" , "Generous" , "Plentiful, quite enough" .)