Cast agrees, get a seasonal gift (6,3)
I believe the answer is:
easter egg
'a seasonal gift' is the definition.
(gift given at Easter)
'cast agrees get' is the wordplay.
'cast' indicates anagramming the letters (letters are dispersed or cast around).
'agrees'+'get'='agreesget'
'agreesget' is an anagram of 'EASTER-EGG'.
(Other definitions for easter egg that I've seen before include "chocolate gift" , "Seasonal fare" , "Edible seasonal symbol" , "Seasonal confection" , "Seasonal present" .)