Brown jelly over fruit (7)
I believe the answer is:
'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'.
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" .)