Brown jelly over fruit (7)
I believe the answer is:
tangelo
'fruit' is the definition.
(I know that tangelo is a fruit)
'brown jelly over' is the wordplay.
'brown' becomes 'tan' (tan is a kind of brown).
'jelly' becomes 'oleg' (I can't justify this - if you can you should believe this answer much more).
'over' says the letters should be written in reverse.
'oleg' in reverse letter order is 'gelo'.
'tan'+'gelo'='TANGELO'
Can you help me to learn more?
(Other definitions for tangelo that I've seen before include "Citrus hybrid - goal net (anag)" , "Hybrid fruit; eat long (anag.)" , "one cross, sour" , "Citrus fruit hybrid" , "sharp cross" .)