During the examination it revealed a chemical (5)

I believe the answer is:

nitre

'chemical' is the definition.
(I know that nitre is a type of nitrate)

'during the examination it revealed a' is the wordplay.
'during' indicates a hidden word.
'NITRE' can be found hidden inside 'examination it revealed a'.

(Other definitions for nitre that I've seen before include "Gunpowder ingredient" , "fertiliser" , "Chemical" , "Inter (anag.)" , "what goes into bangers" .)

I've seen this clue in The Irish Independent.

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