Silvery metal, Y, used in radar technology and and to strengthen some alloys (7)

I believe the answer is:

yttrium

(Other definitions for yttrium that I've seen before include "12 [ELEMENT]" , "Rare earth element" , "Table item" , "Metallic element, symbol Y" , "Silvery metallic element" .)

I've seen this clue in The Guardian.

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