Do the same (5)
I believe the answer is:
ditto
This clue is a double definition.
'do' is the first definition.
(I've seen this before)
'the same' is the second definition.
(I've seen this before)
(Other definitions for ditto that I've seen before include "couple of marks" , "Repeat (instruction)" , "Do alternative" , "Two small marks indicating the same again" , "Mark used to indicate repetition" .)