Refuse to drop off (7)
I believe the answer is:
decline
This clue is a double definition.
'refuse' is the first definition.
(synonyms)
'drop off' is the second definition.
(thesaurus)
'to' acts as a 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" .)