Refuse to deteriorate (7)
I believe the answer is:
decline
This clue is a double definition.
'refuse' is the first definition.
(I know that refuse can be written as decline)
'deteriorate' is the second definition.
(I know that deteriorate is a more specific form of the action decline)
'to' acts as a link.
(Other definitions for decline that I've seen before include "Say no or lose strength" , "Refuse; decay" , "perform grammatical exercise" , "Spurn" , "Evelyn Waugh novel" .)