Unpoetic stuff about border plant (8)
I believe the answer is:
primrose
'plant' is the definition.
(primrose is a kind of plant)
'unpoetic stuff about border' is the wordplay.
'unpoetic stuff' becomes 'prose' (as opposed to poetry).
'about' is an insertion indicator.
'border' becomes 'rim' (I've seen this before).
'prose' going around 'rim' is 'PRIMROSE'.
(Other definitions for primrose that I've seen before include "Yellow spring flower from promiser" , "Pale yellow flower" , "Pale yellow- a primula" , "grows wild" , "Yellowish" .)