Split seconds from whistle, jammy player overturned lead (5)
I believe the answer is:
halve
'split' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for halve that I've seen before include "Bisect" , "Cut down substantially" , "make 10 5 say?" , "Cut into two equal portions" , "Divide into two equal parts" .)