Wisteria, say, increasing on factory (8,5)

I believe the answer is:

climbing plant

'wisteria say' is the definition.
(I know that wistaria is a type of vine)

'increasing on factory' is the wordplay.
'increasing' becomes 'climbing' (climbing is a kind of increasing).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'factory' becomes 'plant' (a manufacturing plant).
'climbing'+'plant'='CLIMBING PLANT'

I've seen this clue in The Daily Express.

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