Vegetable all right in acre hit disastrously (9)
I believe the answer is:
artichoke
'vegetable' is the definition.
(type of vegetable)
'all right in acre hit disastrously' is the wordplay.
'all right' becomes 'ok' (synonyms).
'in' means one lot of letters goes inside another.
'disastrously' indicates an anagram (I've seen this in other clues).
'acre'+'hit'='acrehit'
'acrehit' is an anagram of 'artiche'.
'ok' placed into 'artiche' is 'ARTICHOKE'.
(Other definitions for artichoke that I've seen before include "Thistlelike edible flower head" , "something to eat" , "Edible thistle-like bud" , "Thistle-like plant with edible heads" , "Food item" .)