Area of France that's almost too brill! (6)
I believe the answer is:
alsace
'area of france' is the definition.
(I've seen this before)
'almost too brill' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'too' becomes 'also' (synonyms).
'brill' becomes 'ace' (I've seen this before).
'also' with its final letter taken away is 'als'.
'als'+'ace'='ALSACE'
'that's' acts as a link.
(Other definitions for alsace that I've seen before include "Region in France, occasionally German" , "Region of France, once annexed by Prussia" , "Laces a province in France" , "source of French wines" , "somewhere in France" .)