Expert welcome to probe crux of 'howzat' (4)
I believe the answer is:
whiz
'expert' is the definition.
(whiz is a kind of expert)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for whiz that I've seen before include "chap with a remarkable talent" , "Move rapidly" , "Swish" .)