Liar and cheater beaten up, make peace (5,3,3)
I believe the answer is:
clear the air
'make peace' is the definition.
(to clear the air is to resolve a dispute)
'liar and cheater beaten up' is the wordplay.
'and' is a charade indicator (letters next to each other).
'beaten up' indicates an anagram.
'liar' put after 'cheater' is 'cheaterliar'.
'cheaterliar' anagrammed gives 'CLEAR THE AIR'.
(Other definitions for clear the air that I've seen before include "Relieve a situation of tension" , "Remove tension by settling a misunderstanding" , "Lower the temperature" , "remove any misunderstandings" , "Resolve bad feeling" .)