Plant or tree (6)

I believe the answer is:

orpine

'plant' is the definition.
(orpine is a kind of plant)

'or tree' is the wordplay.
'tree' becomes 'pine' (pine is a kind of tree).
'or'+'pine'='ORPINE'

(Other definitions for orpine that I've seen before include "Purple-flowered stonecrop" , "It may grow upon rock" , "Flowering plant" .)

I've seen this clue in The Telegraph.

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