Writing about border flower (8)
I believe the answer is:
primrose
'flower' is the definition.
(I know that primrose is a type of flower)
'writing about border' is the wordplay.
'writing' becomes 'prose' (prose is ordinary writing as opposed to poetry).
'about' indicates putting letters inside.
'border' becomes 'rim' (both can mean an edge).
'prose' enclosing 'rim' is 'PRIMROSE'.
(Other definitions for primrose that I've seen before include "Pale yellow flower" , "Yellowish" , "Yellow spring flower from promiser" , "something in the bed!" , "Rip morse up to find the flower" .)