Spread around by the perimeter (8)
I believe the answer is:
boundary
'the perimeter' is the definition.
(thesaurus)
'spread around by' is the wordplay.
'spread' indicates anagramming the letters.
'around'+'by'='aroundby'
'aroundby' with letters rearranged gives 'BOUNDARY'.
(Other definitions for boundary that I've seen before include "Perimeter: demarcation" , "march" , "Border (especially in cricket)" , "4 possibly" , "Frontier" .)