Decline to be corrupt (10)
I believe the answer is:
degenerate
This clue is a double definition.
'decline' is the first definition.
(I know that decline is the is a more specific form of the action of degenerate.)
'be corrupt' is the second definition.
(I've seen this before)
'to' acts as a link.
(Other definitions for degenerate that I've seen before include "Unprincipled" , "dishonourable" , "Sexual deviant - grow worse" , "Fallen" , "Corrupt type" .)