Gear Ruby argued occasionally is junk (7)
I believe the answer is:
garbage
'junk' is the definition.
(thesaurus)
'gear ruby argued occasionally' is the wordplay.
'occasionally' indicates alternate letters.
'gear'+'ruby'+'argued'='gearrubyargued'
The alternating letters of 'gearrubyargued' are 'GARBAGE'.
'is' is the link.
(Other definitions for garbage that I've seen before include "Brag about age? - that's rubbish" , "Nonsense!" , "Pop group; rubbish" , "Refuse - a beggar (anag)" , "A beggar? - that may be rubbish" .)