A cook involved in cooking halal food gets very agitated (3,2,1,6)

'involved in cooking halal food gets very agitated' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'a cook' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
'cook' could be 'do' (do can mean to cook) and 'do' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?