Mechanic having benefited from better training (6)

I believe the answer is:

fitter

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'mechanic' is the definition.
(I've seen this before)

I can't explain the remainder of the clue.

(Other definitions for fitter that I've seen before include "Tradesman being in better shape" , "less likely to feel fatigue" , "to get in better shape" , "Worker assembling machinery - more healthy" , "Mechanic" .)

I've seen this clue in The Irish Independent.

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