Rushed round to betray (3,2)
I believe the answer is:
rat on
'betray' is the definition.
('rat on' can be a synonym of 'betray')
'rushed round to' is the wordplay.
'rushed' becomes 'ran'.
'round' indicates putting letters inside.
'ran' placed around 'to' is 'RAT ON'.
(Other definitions for rat on that I've seen before include "Betray" , "shop" , "Give away" , "grass up" , "desert" .)