Tract of grassland left untidy (7)
I believe the answer is:
leaflet
'tract' is the definition.
(I've seen this before)
'grassland left untidy' is the wordplay.
'grassland' becomes 'lea' (lea is a kind of grassland).
'untidy' indicates an anagram.
'left' with letters rearranged gives 'flet'.
'lea'+'flet'='LEAFLET'
'of' is the link.
(Other definitions for leaflet that I've seen before include "Distribute small circulars" , "Single sheet of paper as advert" , "Flyer, bill" , "All feet (anag)" , "very little greenery" .)