Headgear seen on European promontory (4)
I believe the answer is:
cape
'promontory' is the definition.
(both can mean a headland)
'headgear seen on european' is the wordplay.
'headgear' becomes 'cap' (cap is a kind of headgear).
'seen on' means one lot of letters go next to another.
'european' becomes 'e' (abbreviation e.g. EU).
'cap'+'e'='CAPE'
(Other definitions for cape that I've seen before include "Cod, for example" , "Short sleeveless garment" , "Shoulders? They're covered in it" , "Short cloak" , "Outer garment" .)