Flipping exceptional middle of crossword puzzle (5)

I believe the answer is:

rebus

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'puzzle' is the definition.
(type of visual puzzle)

'flipping exceptional middle of crossword' is the wordplay.
'flipping' is a reversal indicator.
'exceptional' becomes 'aberra' (I've seen this in another clue).
'middle of' says to take the centre (I've seen 'middle' mean this).
'crossword' becomes 'bus' (I can't justify this - if you can you should believe this answer much more).
The centre of 'aberra' is 'er'.
'er' in reverse letter order is 're'.
're'+'bus'='REBUS'

Can you help me to learn more?

(Other definitions for rebus that I've seen before include "Puzzle consisting of pictures representing syllables and words" , "that's puzzling" , "Ian Rankin's Scottish detective" , "In Edinburgh, busy" , "Pictorial pun - fictional detective" .)

I've seen this clue in The Telegraph.

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