Circular meadow left to be worked (7)
I believe the answer is:
leaflet
'circular' is the definition.
(thesaurus)
'meadow left to be worked' is the wordplay.
'meadow' becomes 'lea' (I've seen this before).
'to be worked' is an anagram indicator.
'left' anagrammed gives 'flet'.
'lea'+'flet'='LEAFLET'
(Other definitions for leaflet that I've seen before include "Printed handout" , "Small pamphlet" , "It may advertise" , "Single sheet of paper as advert" , "Sheet of paper giving information" .)