Expression of contempt about Liberal nonsense (4)
I believe the answer is:
blah
'nonsense' is the definition.
(blah blah blah)
'expression of contempt about liberal' is the wordplay.
'expression of contempt' becomes 'bah' (I've seen this in another clue).
'about' indicates putting letters inside.
'liberal' becomes 'l' (abbreviation).
'bah' going around 'l' is 'BLAH'.
(Other definitions for blah that I've seen before include "Insipid" , "Bombast" , "bunkum!" , "Stupid 20" , "Dull" .)