Veg from animal park, essential with joint, reportedly (8)
I believe the answer is:
zucchini
'veg' is the definition.
'from animal park essential with joint reportedly' is the wordplay.
I cannot really understand how this works, but
'from' could be 'in' (I've seen this in other clues) and 'in' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for zucchini that I've seen before include "Courgette (US)" , "American courgette" , "green" , "US vegetable" , "Courgette in North America" .)