Hackneyed expression (6)
I believe the answer is:
cliche
'hackneyed expression' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cliche that I've seen before include "Hackneyed idea, plot etc" , "Banal phrase" , "Saying grown familiar through repetition" , "Saying repeated too often" , "Trite phrase" .)