Flowers contributing to Easter Sunday (6)
I believe the answer is:
asters
'flowers' is the definition.
(I know this)
'contributing to easter sunday' is the wordplay.
'contributing to' indicates a hidden word.
'ASTERS' is hidden within 'easter sunday'.
(Other definitions for asters that I've seen before include "Daisylike flowers" , "Otherwise known as Michaelmas daisies" , "Stares oddly at the flowers" , "A rest's a change from flowers" , "Stares at bright flowers" .)