Liberal politician gets in the beer (5)
I believe the answer is:
ample
'liberal' is the definition.
(I've seen this in another clue)
'politician gets in the beer' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'gets in' indicates putting letters inside.
'the beer' becomes 'ale' (type of beer).
'mp' placed into 'ale' is 'AMPLE'.
(Other definitions for ample that I've seen before include "Large, capacious" , "Plentiful; capacious" , "Large, accommodating" , "Big" , "Fairly large" .)