Pierce turned willow spindle's top (4)
I believe the answer is:
stab
'pierce' is the definition.
(I've seen this before)
'turned willow spindle's top' is the wordplay.
'turned' is a reversal indicator.
'willow' becomes 'bat' (willow can mean a cricket bat).
'top' says to take the initial letters (in a down clue, the first letter is top).
The first letter of 'spindles' is 's'.
'bat'+'s'='bats'
'bats' reversed gives 'STAB'.
(Other definitions for stab that I've seen before include "Attack with a dagger" , "Plunge knife into" , "Impale; attempt" , "It could be the death of you" , "Pierce with a knife" .)