Dark greenish-blue (4)
I believe the answer is:
teal
'dark greenish-blue' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for teal that I've seen before include "Dark greenish-blue colour" , "Duck; greenish-blue colour" , "Dark green-blue; duck" , "Type of duck" , "Raise (subject matter)" .)