Wangle kept moaner in line (7)

I believe the answer is:

finagle

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'wangle' is the definition.
(I know that wangle can be written as finagle)

'kept moaner in line' is the wordplay.
'kept moaner' becomes 'nag' (I can't justify this - if you can you should believe this answer much more).
'in' is an insertion indicator.
'line' becomes 'file' (file is a kind of line).
'nag' put into 'file' is 'FINAGLE'.

Can you help me to learn more?

(Other definitions for finagle that I've seen before include "cheat" , "Swindle" , "Dishonestly obtain" .)

I've seen this clue in the Sydney Morning Herald.

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