A peculiar plant (4)

I believe the answer is:

arum

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

'a peculiar' is the wordplay.
'peculiar' becomes 'rum' (synonyms).
'a'+'rum'='ARUM'

(Other definitions for arum that I've seen before include "Cuckoo pint genus" , "genus of plants" , "Plant like cuckoo pint" , "A spirit for a lily" , "Eg, cuckoo pint" .)

I've seen this clue in The Telegraph.

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