Hit wicket in Test (4)
I believe the answer is:
swat
'hit' is the definition.
(swatting is a kind of hitting)
'wicket in test' is the wordplay.
'wicket' becomes 'w'.
'in' means one lot of letters goes inside another.
'test' becomes 'sat' (I can't explain this - if you can you should give a lot more credence to this answer).
'w' put into 'sat' is 'SWAT'.
Can you help me to learn more?
(Other definitions for swat that I've seen before include ".`Twas quite a blow" , "strike smartly" , "'Twas quite a smack" , "Twas something of a blow" , "Smack (a fly?)" .)