Small fish attack pond plant (5-4)

I believe the answer is:

spike-rush

'pond plant' is the definition.
(type of plant found by water)

'small fish attack' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'fish' becomes 'pike' (pike is a kind of fish).
'attack' becomes 'rush' (rush can mean to attack with great force).
's'+'pike'+'rush'='SPIKE-RUSH'

I've seen this clue in The Times.

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