A sign we disapprove of fruit (9)
I believe the answer is:
raspberry
'a sign' is the definition.
(I have seen 'sign of disapproval' mean 'raspberry' so perhaps 'sign' could also mean 'raspberry')
'disapprove of fruit' is the wordplay.
'disapprove of' becomes 'rasp' (I am not sure about this - if you are sure you should believe this answer much more).
'fruit' becomes 'berry' (berry is a kind of fruit).
'rasp'+'berry'='RASPBERRY'
'we' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for raspberry that I've seen before include "Soft fruit" , "Bars Perry from having the fruit" , "Fruit; rude sound" , "Fruit - expression of contempt" , "Derisive sound" .)