This might advertise a little greenery (7)
I believe the answer is:
leaflet
'this might advertise a little' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'greenery' is the wordplay.
I cannot quite see how this works, but
'greenery' could be 'lea' (I've seen this in another clue) and 'lea' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for leaflet that I've seen before include "Printed sheet, flyer" , "It may advertise" , "Bill, pamphlet" , "Single printed sheet" , "All feet (anag)" .)