Serves up a grape juice with a top slice of orange (7)
I believe the answer is:
satsuma
'orange' is the definition.
(I've seen this before)
'serves up a grape juice with a top slice' is the wordplay.
'serves up' shows that the letters should be reversed in order.
'grape juice' becomes 'must' (I've seen this in other clues).
'with' means one lot of letters go next to another.
'top' indicates taking the first letters.
The first letter of 'slice' is 's'.
'a'+'must'+'a'+'s'='amustas'
'amustas' back-to-front is 'SATSUMA'.
'of' acts as a link.
(Other definitions for satsuma that I've seen before include "Easily peeled orange" , "Type of small orange" , "Small variety of orange similar to mandarin" , "A small citrus fruit" , "Loose-skinned fruit" .)