Plant sheath having yellowish-brown area (6)

I believe the answer is:

ochrea

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'plant sheath having yellowish-brown area' is the definition.
I can't judge whether this defines the answer.

'brown area' is the wordplay.
'brown' becomes 'ochre' (I've seen this before).
'area' becomes 'a' (maths abbreviation).
'ochre'+'a'='OCHREA'

Can you help me to learn more?

I've seen this clue in The Independent.

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