Those against scabs covering scar in nippers (11)

I believe the answer is:

pickpockets

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

'those against scabs covering' is the definition.
I can't judge whether this defines the answer.

'scar in nippers' is the wordplay.
'scar' becomes 'pock' (synonyms).
'in' means one lot of letters goes inside another.
'nippers' becomes 'pickets' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'pock' going inside 'pickets' is 'PICKPOCKETS'.

Can you help me to learn more?

I've seen this clue in The Guardian.

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