Sorcerer in fight over jam (7)

I believe the answer is:

warlock

I'm a little stuck... Click here to teach me more about this clue!

'sorcerer' is the definition.
(I've seen this before)

'fight over jam' is the wordplay.
'fight' becomes 'war' (warring is a kind of fighting).
'over jam' becomes 'lock' (I can't justify this - if you can you should give a lot more credence to this answer).
'war'+'lock'='WARLOCK'

'in' is the link.

Can you help me to learn more?

(Other definitions for warlock that I've seen before include "Male magician - British composer, 1894-1930 - low rack (anag)" , "Charmer" , "Cork law about male witch" , "Necromancer" , "Sorcerer" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.