Say no to junk (6)
I believe the answer is:
refuse
This clue is a double definition.
'say no' is the first definition.
(thesaurus)
'junk' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for refuse that I've seen before include "Say no to garbage" , "Deny; rubbish" , "deadwood" , "Decline waste material" , "'Deny, turn down (6)'" .)