Honey contains active ingredient of animal food (4)
I believe the answer is:
meal
'ingredient of animal food' is the definition.
'meal' can be an answer for 'food' (meal is a kind of food). I'm unsure of the 'ingredient of animal' bit.
'honey contains active' is the wordplay.
'honey' becomes 'mel' (Latin name for honey).
'contains' is an insertion indicator.
'active' becomes 'a' (grammatical abbreviation).
'mel' enclosing 'a' is 'MEAL'.
Can you help me to learn more?
(Other definitions for meal that I've seen before include "Breakfast, dinner or supper" , "Coarsely ground grain" , "Edible part of grain or pulse" , "Scoff" , "Grain ground to powder" .)