Drainage construction plant (8)
I believe the answer is:
gardenia
'plant' is the definition.
The answer is an example.
'drainage construction' is the wordplay.
'construction' indicates anagramming the letters (answer constructed from certain letters).
'drainage' anagrammed gives 'GARDENIA'.
(Other definitions for gardenia that I've seen before include "Evergreen" , "Drainage for shrub with white or yellow flowers" , "Fragrant tree or shrub" , "Shrub; drainage (anag.)" , "bloomer!" .)