Fire is green, breaking out orange finally (8)
I believe the answer is:
energise
'fire' is the definition.
('fire'->'energize' is in my internal thesaurus and 'ize'->'ise')
'is green breaking out orange finally' is the wordplay.
'breaking out' indicates anagramming the letters.
'finally' says to take the final letters.
The final letter of 'orange' is 'e'.
'is'+'green'='isgreen'
'isgreen' anagrammed gives 'energis'.
'energis'+'e'='ENERGISE'
(Other definitions for energise that I've seen before include "Give active force" , "To banish inertia" , "Give vitality to" , "give vigour" , "Activate" .)