Circular field left untidy (7)
I believe the answer is:
leaflet
'circular' is the definition.
(I've seen this before)
'field left untidy' is the wordplay.
'field' becomes 'lea' (lea can mean a meadow or field of grass).
'untidy' indicates an anagram.
'left' anagrammed gives 'flet'.
'lea'+'flet'='LEAFLET'
(Other definitions for leaflet that I've seen before include "A pamphlet giving information" , "Distribute small circulars" , "Printed handout" , "Flier" , "Handbill, flyer" .)