Eat in readiness (4)
I believe the answer is:
dine
'eat' is the definition.
(to dine is to eat a meal)
'in readiness' is the wordplay.
'in' says the answer is hidden in the clue.
'DINE' is hidden within 'readiness'.
(Other definitions for dine that I've seen before include "Eat with Enid?" , "Eat main meal" , "Take meal" , "Have supper" , "Take dinner" .)