Excellent ending where there's no beginning (7)
I believe the answer is:
topping
'excellent' is the definition.
(I've seen this before)
'ending where there's no beginning' is the wordplay.
I cannot quite see how this works, but
'ending' could be 'pin' (pin is a kind of ending) and 'pin' is located in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for topping that I've seen before include "garnish for food" , "Absolutely excellent!" , "Sauce; excellent (dated)" , "Garnish - jolly good!" , "A1" .)