Ring-shaped leaflet (8)
I believe the answer is:
circular
I believe this is a double definition.
'ring-shaped' is the first definition.
(synonyms)
'leaflet' is the second definition.
(I know that leaflet can be written as circular)
(Other definitions for circular that I've seen before include "that's passed through a rectangular slot?" , "Round - pamphlet" , "One sort of saw" , "Ring-shaped" , "Rotary" .)