Neat border plant (5)
I believe the answer is:
oxlip
'plant' is the definition.
(oxlip is a kind of plant)
'neat border' is the wordplay.
'neat' becomes 'ox' (I've seen this in other clues).
'border' becomes 'lip' (I've seen this in other clues).
'ox'+'lip'='OXLIP'
(Other definitions for oxlip that I've seen before include "Kind of yellow primrose" , "Eurasian primrose with yellow flowers" , "Flower of the primrose family" , "Type of primula" , "Primrose-cowslip hybrid" .)