Speaking about shade of green (3)
I believe the answer is:
pea
'shade of green' is the definition.
(I've seen this in another clue)
'speaking about' is the wordplay.
'about' indicates a hidden word (the clue goes around or about the answer).
'PEA' is hidden in the letters of 'speaking'.
(Other definitions for pea that I've seen before include "Climbing plant; vegetable" , "Legume" , "Vegetable in a whistle" , "Annual climbing plant with edible seeds" , "Pulse vegetable" .)