Nail one who informs on growth in America (5,5)

I believe the answer is:

spike grass

'growth in america' is the definition.
(type of grass in the Americas)

'nail one who informs on' is the wordplay.
'nail' becomes 'spike' (spike is a kind of nail).
'one who informs' becomes 'grass' (informal term for an informant).
'on' is a charade indicator (letters next to each other).
'spike'+'grass'='SPIKE-GRASS'

I've seen this clue in The Independent.

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