Plant seen in Britain? That's right! (5)
I believe the answer is:
brier
'plant' is the definition.
(brier is a kind of plant)
'britain? that's right' is the wordplay.
'britain?' becomes 'br' (abbreviation).
'that's' becomes 'ie'.
'right' becomes 'r' (common abbreviation).
'br'+'ie'+'r'='BRIER'
'seen in' acts as a link.
(Other definitions for brier that I've seen before include "plant" , "It may be smoked" , "Prickly shrub" , "Thorny bush like the wild rose" , "smoking pipe" .)