Flower in back of plot, unwanted plant (5)
I believe the answer is:
tweed
'flower' is the definition.
(I've seen this before)
'back of plot unwanted plant' is the wordplay.
'back of' indicates one should take the final letters.
'unwanted plant' becomes 'weed' (I've seen this before).
The last letter of 'plot' is 't'.
't'+'weed'='TWEED'
'in' acts as a link.
(Other definitions for tweed that I've seen before include "Rough material" , "flows across a border" , "River on border between England and Scotland" , "Thick woollen cloth - northern river" , "Fabric; river" .)