Member's a Liberal on right (5)
I believe the answer is:
legal
'right' is the definition.
(legal right is a kind of right)
'member's a liberal on' is the wordplay.
'member' becomes 'leg' (I've seen this before**).
'a liberal' becomes 'al' (I've seen this in other clues).
'on' is a charade indicator (letters next to each other).
'leg'+'al'='LEGAL'
(Other definitions for legal that I've seen before include "It's acceptable" , "Compliant with the law" , "Like some tender" , "Permitted by law" , "Within bounds of law" .)