Turning train, too troublesome (8)

I believe the answer is:

rotation

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'turning' is the definition.
(rotation is a kind of turning)

I don't understand how the remainder of the clue works.

(Other definitions for rotation that I've seen before include "Recurring sequence" , "Turn of a wheel" , "Action of turning" , "The action of moving around an orbit" , "Out of control" .)

I've seen this clue in The Telegraph.

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