Rip off Billy or Jacob's coat (6)

I believe the answer is:

fleece

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

'rip off' is the definition.
(fleecing is a kind of ripping off)

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for fleece that I've seen before include "Con" , "Swindle; sheep's coat" , "Sheepskin - rook" , "A target for Jason" , "Jason sought the Golden one" .)

I've seen this clue in The Guardian.

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