Informed about liberal jargon (5)
I believe the answer is:
slang
'jargon' is the definition.
(synonyms)
'informed about liberal' is the wordplay.
'informed' becomes 'sang' (I've seen this in other clues).
'about' is an insertion indicator.
'liberal' becomes 'l' (abbreviation).
'sang' enclosing 'l' is 'SLANG'.
(Other definitions for slang that I've seen before include "Berate" , "Vulgar language" , "common language" , "Any class's jargon" , "... to scold" .)