"Resigning" in service terminology? (9,4,4)

I believe the answer is:

deserting ones post

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'service terminology?' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'resigning in' is the wordplay.
I cannot really understand how this works, but
'in' is within the answer.
This may be the basis of clue (or it may be nonsense).

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