Unhappy in serious adversity (3)

I believe the answer is:

sad

'unhappy' is the definition.
(associated in meaning)

'in serious adversity' is the wordplay.
'in' says the answer is hidden in the clue.
'SAD' can be found hidden inside 'serious adversity'.

(Other definitions for sad that I've seen before include "Melancholy, depressed" , "Dejected" , "Winter blues, initially" , "Unfortunate" , "Melancholy, downhearted" .)

I've seen this clue in the Evening Standard.

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