Overused, of dubious merit now (8)
I believe the answer is:
timeworn
'overused' is the definition.
(timeworn can mean overused or cliched)
'dubious merit now' is the wordplay.
'dubious' is an anagram indicator.
'merit'+'now'='meritnow'
'meritnow' is an anagram of 'TIMEWORN'.
'of' is the link.
(Other definitions for timeworn that I've seen before include "Familiar through overuse" , "Decayed by long use" , "Overfamiliar through overuse" , "Tired" , "Out of date" .)