Extent of shooting area (5)
I believe the answer is:
range
I believe this clue is a double definition.
'extent' is the first definition.
(I know that range is a type of extent)
'shooting area' is the second definition.
(shooting range)
'of' acts as a link.
(Other definitions for range that I've seen before include "Selection" , "Distance aircraft can travel" , "Andes or Rockies, perhaps?" , "Compass - scope" , "Limits - scope" .)