Green duck full of energy (5)
I believe the answer is:
olive
'green' is the definition.
(olive green is a kind of green)
'duck full of energy' is the wordplay.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'full of energy' becomes 'live' (I am not sure about this - if you are sure you should believe this answer much more).
'o'+'live'='OLIVE'
Can you help me to learn more?
(Other definitions for olive that I've seen before include "Oil producer" , "girl" , "This branch is offered to show peace" , "Greyish-green; fruit" , "Yellowy-green colour and fruit" .)