Biggest gear broken on MOT? (8)

I believe the answer is:

greatest

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'biggest' is the definition.
('great' can be similar in meaning to 'big')

'gear broken on mot?' is the wordplay.
'broken' indicates anagramming the letters.
'on mot?' becomes 'test' (I can't justify this - if you can you should believe this answer much more).
'gear' anagrammed gives 'grea'.
'grea'+'test'='GREATEST'

Can you help me to learn more?

(Other definitions for greatest that I've seen before include "Biggest and best, like Muhammad Ali" , "Not to be surpassed" , "Largest or most distinguished" , "Best-ever" , "Highest in quality or in quantity" .)

I've seen this clue in The Sun.

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