Preserve in gelatine (3)
I believe the answer is:
tin
'preserve' is the definition.
(I know that tin is a more specific form of the action preserve)
'in gelatine' is the wordplay.
'in' says the answer is hidden in the clue.
'TIN' is hidden in the letters of 'gelatine'.
(Other definitions for tin that I've seen before include "Silvery-white metal used in cans" , "Silver-white metal, used to make cans" , "loaf of bread" , "Element, symbol Sn" , "Earnings" .)