Vegetable wine's gone over seat (7)
I believe the answer is:
cassava
'vegetable' is the definition.
(I know that cassava is a type of root vegetable)
'wine's gone over seat' is the wordplay.
'wine's gone' becomes 'cava' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'over' indicates putting letters inside.
'seat' becomes 'ass' (synonyms).
'cava' going around 'ass' is 'CASSAVA'.
Can you help me to learn more?
(Other definitions for cassava that I've seen before include "tree" , "Tropical American starchy plant" , "Edible tropical root" , "Staple food, the source of tapioca" , "starchy type" .)