Undiscerning Liberal in fix (5)
I believe the answer is:
blind
'undiscerning' is the definition.
(thesaurus)
'liberal in fix' is the wordplay.
'liberal' becomes 'l' (abbreviation).
'in' is an insertion indicator.
'fix' becomes 'bind' (binding is a kind of fixing**).
'l' going within 'bind' is 'BLIND'.
(Other definitions for blind that I've seen before include "Unobserving" , "without a way out" , "Sightless" , "cover-up" , "Unable to observe" .)