Tendency to be corrupt (4)
I believe the answer is:
bent
I believe this clue is a double definition.
'tendency' is the first definition.
(bent can mean a propensity or tendency)
'be corrupt' is the second definition.
(I've seen this before)
'to' acts as a link.
(Other definitions for bent that I've seen before include "Propensity, preference" , "Angled; corrupt" , "Crooked - inclination" , "Crooked - tendency" , "Angled; grass" .)