Shopkeeper is coarser in speech (6)
I believe the answer is:
grocer
'shopkeeper' is the definition.
(I know that grocer is a type of shopkeeper)
'coarser in speech' is the wordplay.
'coarser' becomes 'grosser' ('gross' can be a synonym of 'coarse').
'in speech' indicates a 'sounds like' (homophone) clue.
'grosser' sounds like 'GROCER'.
'is' is the link.
(Other definitions for grocer that I've seen before include "Shopkeeper who sells food and household goods" , "Shopkeeper who sells food and household stores" , "Seller of food and household supplies" , "Seller of household items and food" , "Food merchant" .)