Waving e.g. banner about source of exotic vegetable (5,4)
I believe the answer is:
green bean
'vegetable' is the definition.
(green bean is a type of vegetable)
'waving e g banner about source of exotic' is the wordplay.
'waving' indicates anagramming the letters (letters wave around).
'about' means one lot of letters goes inside another.
'source of' indicates taking the first letters.
The first letter of 'exotic' is 'e'.
'e'+'g'+'banner'='egbanner'
'egbanner' with letters rearranged gives 'grenbean'.
'grenbean' enclosing 'e' is 'GREEN BEAN'.
(Other definitions for green bean that I've seen before include "runner?" , "French" , "Plant" , "Vegetable" .)