Upcoming fashion — chain of shops to provide special footwear (10,5)
I believe the answer is:
wellington boots
'special footwear' is the definition.
(boots worn in muddy areas)
'upcoming fashion chain of shops' is the wordplay.
'upcoming' becomes 'welling' (well can mean to come up).
'fashion' becomes 'ton' (term for style or fashion).
'chain of shops' becomes 'Boots' (chain of health shops).
'welling'+'ton'+'boots'='WELLINGTON BOOTS'
'to provide' acts as a link.
(Other definitions for wellington boots that I've seen before include "calves protected by these?" , "rubber items? - with 24a" , "Footwear" .)