Scope of old shelter (6)
I believe the answer is:
extent
'scope' is the definition.
(I've seen this before)
'old shelter' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'shelter' becomes 'tent' (canvas shelter).
'ex'+'tent'='EXTENT'
'of' is the link.
(Other definitions for extent that I've seen before include "Area covered by something" , "stretch" , "Area something covers" , "The size or scale of something" , "Degree or spread" .)