Crossword Genius

Tons come down to exercise (5)

Ross

I believe the answer is:

train

'exercise' is the definition.
(training is a kind of exercising)

'tons come down' is the wordplay.
'tons' becomes 't'.
'come down' becomes 'rain' (raining is a kind of coming down).
't'+'rain'='TRAIN'

'to' is the link.

(Other definitions for train that I've seen before include "union's lengthy item" , "Number of animals moving in a line, like camels" , "Rail service" , "Retinue; sequence" , "Do exercises" .)

I've seen this clue in The Times.
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