Welshman has change of heart, finding betting odds (5)

I believe the answer is:

evens

I'm a little stuck... Click here to teach me more about this clue!

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

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

(Other definitions for evens that I've seen before include "Half a chance" , "Balanced odds" , "less likely than 27 [ODDS-ON]" , "Fifty-fifty odds" , "straight bet" .)

I've seen this clue in The Times.

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