Chase hard with the rest in front (4)
I believe the answer is:
etch
'chase' is the definition.
(I've seen this before)
'hard with the rest in front' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'with the rest' becomes 'etc' (et cetera).
'in front' means one lot of letters go next to another.
'h' put after 'etc' is 'ETCH'.
(Other definitions for etch that I've seen before include "Engrave (glass/metal)" , "Inscribe" , "Chase" , "Mark" , "Incribe" .)