Flight circling in airspace trials small buggy (6,9)

I believe the answer is:

spiral staircase

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'flight circling in' is the definition.
'spiral staircase' can be an answer for 'flight' (I've seen this before). I am not sure about the 'circling in' bit.

'airspace trials small buggy' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'buggy' indicates anagramming the letters.
'airspace'+'trials'+'s'='airspacetrialss'
'airspacetrialss' anagrammed gives 'SPIRAL STAIRCASE'.

Can you help me to learn more?

(Another definition for spiral staircase that I've seen is " Not a direct flight".)

I've seen this clue in The Independent.

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