Say no to garbage (6)
I believe the answer is:
refuse
I believe this is a double definition.
'say no' is the first definition.
(I've seen this before)
'to garbage' is the second definition.
(synonyms)
(Other definitions for refuse that I've seen before include "Decline to take the rubbish" , "Don't take the rubbish" , "Turn down; waste" , "Say no to garbage" , "Decline to accept - rubbish" .)