Grub in a merino sheep's innards (4)
I believe the answer is:
nosh
'grub' is the definition.
(I've seen this before)
'in a merino sheep's innards' is the wordplay.
'in' indicates a hidden word.
'NOSH' can be found hidden inside 'merino sheeps innards'.
(Other definitions for nosh that I've seen before include "Food (sl.)" , "Fare" , "(Eat) a snack" , "cuisine" , "Eat (sl.)" .)