Vegetables speak of Jack's vine (9)
I believe the answer is:
beanstalk
'jack's vine' is the definition.
The answer and definition can be both plants as well as being singular nouns.
Maybe there's a link between them I don't understand?
'vegetables speak' is the wordplay.
'vegetables' becomes 'beans' (bean is a kind of vegetable).
'speak' becomes 'talk' (synonyms).
'beans'+'talk'='BEANSTALK'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for beanstalk that I've seen before include "[FAIRY STORY REF]" , "Jack's impulse buy" , "Leguminous stem that Jack climbed" , "Jack cut it down" , "epitome of rapid growth" .)