Singing hypocritical words, outwardly mostly inferior (3,5)
I believe the answer is:
bel canto
'singing' is the definition.
(bel canto is a kind of singing)
'hypocritical words outwardly mostly inferior' is the wordplay.
'hypocritical words' becomes 'cant' (cant can mean hypocritical talk).
'outwardly' is an insertion indicator (some letters go outside others).
'mostly' means to remove the last letter.
'inferior' becomes 'below' (I've seen this before).
'below' with its last letter taken off is 'belo'.
'cant' going inside 'belo' is 'BEL CANTO'.
(Other definitions for bel canto that I've seen before include "Lyrical operatic style" , "Type of singing" , "Style of operatic singing, as that of Callas, say" , "Operatic singing style - noble act (anag)" , "Lyrical style of opera singing" .)