Dine in Meath (3)
I believe the answer is:
eat
'dine' is the definition.
(eat a meal)
'in meath' is the wordplay.
'in' says the answer is hidden in the clue.
'EAT' is hidden in the letters of 'meath'.
(Other definitions for eat that I've seen before include "Have 23d [MEAL]" , "Worry" , "Take food" , "Consume (food)" , "Break bread" .)