Fruit to put around sort of cake (7)
I believe the answer is:
tangelo
'fruit' is the definition.
(I know that tangelo is a fruit)
'to put around sort of cake' is the wordplay.
'put around' indicates putting letters inside.
'sort of cake' becomes 'angel'.
'to' enclosing 'angel' is 'TANGELO'.
(Other definitions for tangelo that I've seen before include "sharp cross" , "Mixed fruit" , "fruitful merger?" , "one cross, sour" , "Citrus hybrid - goal net (anag)" .)