Politician drowned in beer? That's quite enough! (5)
I believe the answer is:
ample
'quite enough' is the definition.
(I've seen this in another clue)
'politician drowned in beer?' is the wordplay.
'politician' becomes 'MP' (Member of Parliament).
'drowned in' indicates putting letters inside (I've seen this in other clues).
'beer?' becomes 'ale' (type of beer).
'mp' put into 'ale' is 'AMPLE'.
'that's' is the link.
(Other definitions for ample that I've seen before include "Generous" , "Big" , "Large, accommodating" , "Fully enough" , "Fairly large" .)