Salver of betrayal (4)
I believe the answer is:
tray
'salver' is the definition.
(I've seen this before)
'of betrayal' is the wordplay.
'of' says the answer is hidden in the clue.
'TRAY' can be found hidden inside 'betrayal'.
(Other definitions for tray that I've seen before include "Kitchen carrier" , "Item used for carrying food and drink" , "Salver" , "Flat plate for carrying things" , "Carrying container" .)