Dismissed poor service in store (6)
I believe the answer is:
outlet
'store' is the definition.
(thesaurus)
'dismissed poor service' is the wordplay.
'dismissed' becomes 'out' (I've seen this before).
'poor service' becomes 'let' (tennis).
'out'+'let'='OUTLET'
'in' acts as a link.
(Other definitions for outlet that I've seen before include "Discharge pipe" , "Opening permitting release" , "Retail point" , "Opening, vent." , "Shop (retail)" .)