Catty remark about commercial grassland (6)
I believe the answer is:
meadow
'grassland' is the definition.
(I know that meadow is a type of grassland)
'catty remark about commercial' is the wordplay.
'catty remark' becomes 'meow' (I've seen this before).
'about' indicates putting letters inside.
'commercial' becomes 'ad' (abbreviation for advertisement).
'meow' placed around 'ad' is 'MEADOW'.
(Other definitions for meadow that I've seen before include "somewhere grassy" , "Grassed field" , "Paddock" , "Pasture" , "Grassy field" .)