In hand, most impressive (3,6)
I believe the answer is:
top banana
'in hand' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for top banana that I've seen before include "Star comedian" , "Boss (slang)" , "Best of the bunch!" , "first on hand?" , "head" .)