Greenhouse gas has park warden huffy in the end (8)
I believe the answer is:
orangery
'greenhouse' is the definition.
(I know that orangery is a type of greenhouse)
'gas has park warden huffy in the end' is the wordplay.
'gas' becomes 'O' (chemical symbol for oxygen).
'has' is a charade indicator (letters next to each other).
'park warden' becomes 'ranger' (I've seen this before).
'in the end' indicates one should take the final letters.
The last letter of 'huffy' is 'y'.
'o'+'ranger'+'y'='ORANGERY'
(Other definitions for orangery that I've seen before include "Citrus hothouse" , "fruit source" , "Plant-house" , "Greenhouse often with stately home" , "Building for growing fruit from warmer climes" .)