Scarper with key copy (6)
I believe the answer is:
escape
'scarper' is the definition.
(I know that scarper can be written as escape)
'with key copy' is the wordplay.
'with' says to put letters next to each other.
'key' becomes 'esc' ('Escape' key on a computer keyboard).
'copy' becomes 'ape' (ape can mean to copy or imitate).
'esc' put next to 'ape' is 'ESCAPE'.
(Other definitions for escape that I've seen before include "Duck" , "Break loose, get away" , "Get out of captivity, go over the wall" , "Gain freedom" , "Elude; leakage" .)