Refuse to drop off (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)
'drop off' is the second definition.
(thesaurus)
'to' is the link.
(Other definitions for decline that I've seen before include "Diminish; deteriorate" , "Say no or lose strength" , "perform grammatical exercise" , "Turn down; deteriorate" , "Refuse - to go down" .)