Best to expose swindle (5)
I believe the answer is:
outdo
'best' is the definition.
('outdo' can be a synonym of 'best')
'expose swindle' is the wordplay.
'expose' becomes 'out' (outing is a kind of exposing).
'swindle' becomes 'do'.
'out'+'do'='OUTDO'
'to' acts as a link.
(Other definitions for outdo that I've seen before include "Be better in performance (than another person)" , "Overtake" , "Surpass, go one better than" , "Surpass - overshadow - excel" , "Br superior to (someone)" .)