Somewhat vulgar denial that can be cultivated (8)
I believe the answer is:
gardenia
'can be cultivated' is the definition.
(the plant gardenia may be cultivated)
'somewhat vulgar denial that' is the wordplay.
'somewhat' indicates a hidden word.
'GARDENIA' can be found hidden inside 'vulgar denial that'.
(Other definitions for gardenia that I've seen before include "bloomer!" , "Shrub with fragrant flowers - in Grade A (anag)" , "Fragrant tree or shrub" , "Fragrant shrub, red again (anag.)" , "Drainage (anag) -- plant" .)