Sold grass, keeping in shadow (8)
I believe the answer is:
retailed
'sold' is the definition.
(retailing is a kind of selling)
'grass keeping in shadow' is the wordplay.
'grass' becomes 'reed' (type of grass plant).
'keeping' means one lot of letters goes inside another.
'in shadow' becomes 'tail' (both can mean to follow someone. I am not sure about the 'in' bit.).
'reed' placed around 'tail' is 'RETAILED'.
Can you help me to learn more?
(Another definition for retailed that I've seen is " Sold".)