Competitor a rail crash could dishearten? (5)

I believe the answer is:

rival

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'competitor' is the definition.
(I know that competitor can be written as rival)

I cannot understand how the remainder of the clue works.

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(Other definitions for rival that I've seen before include "Person in direct competition" , "Competitor; be as good as" , "Emulate" , "Adversary, antagonist" , "Challenger, competitor" .)

I've seen this clue in the Evening Standard.

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