Informed about liberal jargon (5)
I believe the answer is:
slang
'jargon' is the definition.
(I know that jargon can be written as slang)
'informed about liberal' is the wordplay.
'informed' becomes 'sang' (I've seen this in other clues).
'about' means one lot of letters goes inside another.
'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" .)