The same thing again (5)
I believe the answer is:
ditto
'the same thing again' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ditto that I've seen before include "Two dots indicating the same again" , "Two small marks indicating the same again" , "Repeat the word above" , "Do alternative" , "Notation meaning the same again" .)