Betray public official, almost retired (3,2)
I believe the answer is:
rat on
'betray' is the definition.
('rat on' can be a synonym of 'betray')
'public official almost retired' is the wordplay.
'public official' becomes 'notary' (I've seen this before).
'almost' means to remove the last letter (most of the word but not all of it).
'retired' says the letters should be written in reverse.
'notary' with its final letter taken away is 'notar'.
'notar' backwards is 'RAT ON'.
(Other definitions for rat on that I've seen before include "Betray" , "Give away" , "grass up" , "desert" , "shop" .)