Crossword Genius

2-D shape I'm not sure is for group of plants (9)

Ross

I believe the answer is:

polygonum

'is for group of plants' is the definition.

'2-d shape i'm not sure' is the wordplay.
'2-d shape' becomes 'polygon'.
'i'm not sure' becomes 'um' (expression of hesitation).
'polygon'+'um'='POLYGONUM'

(Another definition for polygonum that I've seen is " knotweed".)

I've seen this clue in The Guardian.
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