Devious few do act false (3-5)
I believe the answer is:
two-faced
'false' is the definition.
(thesaurus)
'devious few do act' is the wordplay.
'devious' indicates an anagram.
'few'+'do'+'act'='fewdoact'
'fewdoact' anagrammed gives 'TWO-FACED'.
(Other definitions for two-faced that I've seen before include "Treacherous" , "Deceitful like Janus, Roman god of doors" , "Deceitful, double-dealing" , "Double-meaning" , "Double-dealing, like Janus?" .)