Aim to have unconfined lions in big top's opening (9)

I believe the answer is:

intention

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'aim' is the definition.
(I know that aim can be written as intention)

'unconfined lions in big top's opening' is the wordplay.
'unconfined lions in' becomes 'inion' (I can't explain this - if you can you should believe this answer much more).
'big top' becomes 'tent' (I've seen this in another clue).
'opening' is an insertion indicator (some letters open a gap in others).
'inion' enclosing 'tent' is 'INTENTION'.

'to have' acts as a link.

Can you help me to learn more?

(Other definitions for intention that I've seen before include "Aim, objective" , "Plan, purpose" , "end" , "Design" , "Aim, purpose" .)

I've seen this clue in The Telegraph.

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