Messengers delivering footwear (7)
I believe the answer is:
runners
I believe this clue is a double definition.
'messengers' is the first definition.
(I know this)
'footwear' is the second definition.
(I know that runners is a type of athletic shoe)
'delivering' is the link.
(Other definitions for runners that I've seen before include "Joggers" , "Shoots" , "Horizontal branches that produce new plants" , "Horizontal branchs that produce new plants" , "messengers?" .)