Fish, 1000 in shop (6)
I believe the answer is:
salmon
'fish' is the definition.
(salmon is a kind of fish)
'1000 in shop' is the wordplay.
's000' becomes 'm' ('m' can be a synonym of 's000').
'in' indicates putting letters inside.
'shop' becomes 'salon' (salon is a kind of shop**).
'm' placed inside 'salon' is 'SALMON'.
(Other definitions for salmon that I've seen before include "pink-orange in colour" , "Pale pinkish orange colour" , "Underwater swimmers" , "Food fish; pink shade" , "Pink-fleshed fish" .)