Sweet william (4)
I believe the answer is:
pink
'sweet william' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pink that I've seen before include "one's found in bed" , "Colour; garden plant" , "Alcoholic hallucinations" , "Knock (of engine) - garden flower" , "Cut wavy edge on, plant" .)