A mountain area in France (5)
I believe the answer is:
alpha
'a mountain area in france' is the definition.
I can't judge whether this definition defines the answer.
'mountain area in france' is the wordplay.
'mountain' becomes 'alp' (alp is a kind of mountain).
'area in france' becomes 'ha' (short for hectare, unit of area with a French name).
'alp'+'ha'='ALPHA'
(Other definitions for alpha that I've seen before include "Beginning" , "very good rating" , "Brilliant star" , "Greek vowel" , "First letter of the Greek alphabet" .)