Sensible quota for a Liberal (8)
I believe the answer is:
rational
'sensible' is the definition.
('rational' is associated in meaning with 'sensible')
'quota for a liberal' is the wordplay.
'quota' becomes 'ration' (I've seen this before).
'for' is a charade indicator (letters next to each other).
'a liberal' becomes 'al' (I've seen this in other clues).
'ration'+'al'='RATIONAL'
(Other definitions for rational that I've seen before include "Sound; sensible" , "Having common sense or reason" , "Reasonable, logical" , "Not absurd" , "Consistent with logic" .)