About to copy cloak (4)
I believe the answer is:
cape
'cloak' is the definition.
(I know that cape is a type of cloak)
'about to copy' is the wordplay.
'about' becomes 'c' (abbreviation for 'circa').
'to copy' becomes 'ape' (ape can mean to copy or imitate).
'c'+'ape'='CAPE'
(Other definitions for cape that I've seen before include "An old cloak or a headland" , "Covering for the shoulders" , "Cloak, robe" , "Headland - garment" , "Horn or Good Hope - cloak" .)