Best escape at the highest level (9)

I believe the answer is:

topflight

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'best' is the definition.
Both the answer and definition are adjectives.
Maybe they are linked in a way I don't understand?

'escape at the highest level' is the wordplay.
'escape' becomes 'flight' (synonyms).
'at' means one lot of letters go next to another (I've seen this in other clues).
'the highest level' becomes 'top' (I've seen this in another clue).
'flight' put after 'top' is 'TOPFLIGHT'.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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