Generous porter letting politician in (5)
I believe the answer is:
ample
'generous' is the definition.
(similar in meaning)
'porter letting politician in' is the wordplay.
I cannot quite understand how this works, but
'politician' could be 'mp' (Member of Parliament) and 'mp' is found within the answer.
'porter' could be 'ale' (I've seen this in another clue) and 'ale' is present in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for ample that I've seen before include "Easily sufficient" , "Adequate" , "Quite sufficient, more than enough" , "Plenty, more than enough" , "Full-figured" .)