No secret round green (5)
I believe the answer is:
overt
'no secret' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?
'round green' is the wordplay.
'round' becomes 'o' (round can mean a round object).
'green' becomes 'vert' (I've seen this before).
'o'+'vert'='OVERT'
Can you help me to learn more?
(Other definitions for overt that I've seen before include "Voter (anag.)" , "Open and undisguised" , "Openly displayed" , "not disguised" , "Not concealed - public" .)