It could be blooming hard in yacht at sea (8)
I believe the answer is:
hyacinth
'it could be blooming' is the definition.
(type of flower)
'hard in yacht at sea' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'at sea' is an anagram indicator.
'in'+'yacht'='inyacht'
'inyacht' with letters rearranged gives 'yacinth'.
'h'+'yacinth'='HYACINTH'
(Other definitions for hyacinth that I've seen before include "Fragrantly-flowered bulb" , "Bulb-based plant with fragrant bell-shaped flowers" , "Flower, in an achy hint" , "Popular flower grown from bulb" , "Spring flower" .)