Marks & Spenser talk about introducing new stores initially (6)
I believe the answer is:
stains
'marks' is the definition.
('stain' can be a synonym of 'mark')
'spenser talk about introducing new stores initially' is the wordplay.
'initially' suggests taking the first letters.
The initial letters of 'spenser talk about introducing new stores' is 'STAINS'.
(Other definitions for stains that I've seen before include "Discolours or dyes wood" , "Discolorations or dirt marks" , "Black marks for saints" , "Discolorations or blemishes" , "Sullies" .)