Unusual trace elements may do this (5)

I believe the answer is:

react

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'elements may do this' is the definition.
The definition suggests a singular noun but the answer is not.

'unusual trace' is the wordplay.
'unusual' indicates an anagram.
'trace' is an anagram of 'REACT'.

Can you help me to learn more?

(Other definitions for react that I've seen before include "Act as opponent" , "Retaliate" , "What a chemical might do" , "Perform again" , "Change chemically" .)

I've seen this clue in The Times.

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