Phoney (9)
'phoney' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for insincere that I've seen before include "Hollow" , "Not genuine, hypocritical" , "Less than honest" , "Not genuine, feigned" , "Dishonest" .)
'phoney' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for bogus that I've seen before include "that's not real" , "Pretended" , "Not genuine, sham" , "Sham, phoney" , "Not true" .)