Hat on European's head (4)
I believe the answer is:
cape
'head' is the definition.
(thesaurus)
'hat on european's' is the wordplay.
'hat' becomes 'cap' (I've seen this before**).
'on' is a charade indicator (letters next to each other).
'european' becomes 'e' (abbreviation e.g. EU).
'cap'+'e'='CAPE'
(Other definitions for cape that I've seen before include "Florida space flight centre" , "Sleeveless garment like a cloak" , "Wrath, say" , "Garment - promontory" , "Cloak; head" .)