Ancient region of Western Europe (4)
I believe the answer is:
gaul
'ancient region of western europe' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gaul that I've seen before include "Ancient region of France/Belgium in Caesar's time" , "Asterix, for example" , "Caesar's name for old France" , "Name given for ancient France from Celtic times" , "old country" .)