Range of former shelter (6)
I believe the answer is:
'range' is the definition.
(I've seen this in another clue)
'former shelter' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'shelter' becomes 'tent' (canvas shelter).
'of' is the link.
(Other definitions for extent that I've seen before include "Measure" , "Compass, scope" , "stretch" , "Area something covers" , "Range or scope of something" .)