Plant unknown in modern times — British one (6)
I believe the answer is:
adzuki
'plant' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'unknown in modern times british one' is the wordplay.
'unknown' becomes 'z' (algebra).
'in' is an insertion indicator.
'modern times' becomes 'ad' (I've seen this in other clues).
'british' becomes 'uk' (I've seen this in other clues**).
'one' becomes 'i' (Roman numeral).
'ad'+'uk'='aduk'
'z' inserted into 'aduk' is 'adzuk'.
'adzuk'+'i'='ADZUKI'
Can you help me to learn more?
(Other definitions for adzuki that I've seen before include "type of beans" , "Small edible bean (z, not s)" , "Type of bean (Z, not S)" , "Bean plant" .)