Revert to bad habits, installing Liberal in seat (9)
I believe the answer is:
backslide
'revert to' is the definition.
(thesaurus)
'bad habits installing liberal in seat' is the wordplay.
I cannot really understand how this works, but
'liberal' could be 'l' (abbreviation) and 'l' is found in the answer.
'seat' could be 'backside' (synonyms) and 'backside' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for backslide that I've seen before include "Degenerate" , "Relapse into bad ways" , "Lapse into bad habits" .)