How one might defend being devious about a ticket seller (7)

I believe the answer is:

stoutly

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

'how one might defend' is the definition.
I can't judge whether this definition defines the answer.

'devious about a ticket seller' is the wordplay.
'devious' becomes 'sly' (I've seen this in another clue).
'about' is an insertion indicator.
'a ticket seller' becomes 'tout' (as in a ticket tout).
'sly' enclosing 'tout' is 'STOUTLY'.

'being' acts as a link.

Can you help me to learn more?

(Another definition for stoutly that I've seen is " Bravely".)

I've seen this clue in the Evening Standard.

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