Answer: whiz

AnswerCrossword Clue
WHIZLeak
WHIZSomeone very capable: Slang.
WHIZHum.
WHIZVery able one: Slang.
WHIZCorker.
WHIZGenius: Slang.
WHIZProdigy: Slang.
WHIZZip
WHIZBrainiac
WHIZShoot (by)
WHIZZoom
WHIZTalented expert
WHIZType of kid
WHIZGifted one
WHIZReally quick study
WHIZKnow-it-all
WHIZFly (by)
WHIZGenius
whizto move with a humming, buzzing, or hissing sound
whizwhizzing sound
whizto hum, whir, or hiss like a speeding object (as an arrow or ball) passing through air
WHIZProficient one
WHIZAce
WHIZPhenom
WHIZPro
WHIZExpert
WHIZCheez ..: Kraft spread
WHIZCrackerjack
WHIZGee follower
WHIZMaster
WHIZExpert, slangily
WHIZSuperskillful one
WHIZVirtuoso
WHIZWise kid?
WHIZCheez ...
WHIZHumdinger
WHIZRocket scientist, say
WHIZ... kid: young genius
WHIZExpert, in slang
WHIZTalented one, slangily