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' means one lot of letters go next to another.
'park warden' becomes 'ranger' (I've seen this before).
'in the end' suggests the final letters.
The final 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" .)