By end of lengthy cycle, I run into mongrel element (7)

I believe the answer is:

yttrium

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

'element' is the definition.
(I know that yttrium is a type of metal)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for yttrium that I've seen before include "Table item" , "Chemical element; um, try it (anag.)" , "Metallic element, symbol Y" , "Rare earth element" , "Silvery metallic element" .)

I've seen this clue in the Sydney Morning Herald.

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