Area of variation (5)
I believe the answer is:
range
'area of variation' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for range that I've seen before include "Cowboy song 'Home on the . . . . .'" , "Area of variation" , "Cooking stove or location for target practice" , "practise shooting here" , "Chain of mountains" .)