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 see how this works, but
'liberal' could be 'l' (abbreviation) and 'l' is found in the answer.
'seat' could be 'backside' (synonyms) and 'backside' is located in the leftover letters.
No letters remain.
This explanation may well be incorrect...
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" .)
