Ahead, Sir, probably the scatterbrains (8)

I believe the answer is:

airheads

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

'scatterbrains' is the definition.
(I've seen this in another clue)

'ahead sir probably' is the wordplay.
'ahead sir' anagrams to 'AIRHEADS'.
But, I am unsure how this is indicated.

'the' acts as a link.

Can you help me to learn more?

(Other definitions for airheads that I've seen before include "unthinking people" , "Feather-brains" , "Dopes" , "military bases" , "Idiots" .)

I've seen this clue in the Sydney Morning Herald.

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