When not working, given to being casual (3-6)

I believe the answer is:

off-handed

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'casual' is the definition.
Both the definition and answer are adjectives.
Maybe there's a link between them I don't understand?

'when not working given to' is the wordplay.
'when' becomes 'handed' (I can't explain this - if you can you should believe this answer much more).
'not working' becomes 'off' (I've seen this before).
'given to' says to put letters next to each other.
'handed' put after 'off' is 'OFF-HANDED'.

'being' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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