Flowers required for Easter service (6)
I believe the answer is:
'flowers' is the definition.
(aster is a type of flower)
'required for easter service' is the wordplay.
'required for' indicates a hidden word.
'ASTERS' can be found hidden inside 'easter service'.
(Other definitions for asters that I've seen before include "Christmas daisies" , "Otherwise known as Michaelmas daisies" , "Stares at bright flowers" , "Stares oddly at the flowers" , "Stares around at the flowers" .)