Whipped cream perhaps ranks as best (7)
I believe the answer is:
topping
'whipped cream perhaps' is the definition.
(I know that whipped cream is a type of topping)
'ranks as best' is the wordplay.
I cannot really see how this works, but
'as' could be 'in' (I've seen this in other clues) and 'in' is found within the answer.
'best' could be 'top' (top can mean the very best) and 'top' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for topping that I've seen before include "Garnish - jolly good!" , "Garnish - splendid!" , "Polishing off" , "Excellent; eg, icing" , "A1" .)