Comic hero's endless treks around shops (12)
I believe the answer is:
supermarkets
'shops' is the definition.
(I've seen this before)
'comic hero's endless treks around' is the wordplay.
'comic hero' becomes 'Superman' (comic book character).
'endless' means to remove the last letter.
'around' indicates an anagram.
'superman' with its last letter removed is 'superma'.
'treks' anagrammed gives 'rkets'.
'superma'+'rkets'='SUPERMARKETS'
(Other definitions for supermarkets that I've seen before include "Food stores" , "Large stores" , "Large shops" , "Food emporia" .)