Militant is awful cad and liar (7)
I believe the answer is:
radical
'militant' is the definition.
(I've seen this before)
'awful cad and liar' is the wordplay.
'awful' is an anagram indicator.
'and' is a charade indicator (letters next to each other).
'cad' put after 'liar' is 'liarcad'.
'liarcad' anagrammed gives 'RADICAL'.
'is' is the link.
(Other definitions for radical that I've seen before include "Militant" , "Total" , "Going to the roots, fundamental as change may be" , "Person with extreme political views" , "Going to the root" .)