About to copy headland (4)
I believe the answer is:
cape
'headland' is the definition.
(I've seen this in another clue)
'about to copy' is the wordplay.
'about' becomes 'c' (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 "Shawl" , "Outer garment" , "Sleeveless garment like a cloak" , "Cloak or headland (4)" , "Sleeveless overgarment" .)