Correct, sport — ion is a particle (8)
I believe the answer is:
positron
'particle' is the definition.
(I know that positron is a type of antilepton)
'correct sport ion' is the wordplay.
'correct' is an anagram indicator.
'sport'+'ion'='sportion'
'sportion' with letters rearranged gives 'POSITRON'.
'is a' acts as a link.
(Other definitions for positron that I've seen before include "possible contributor to annihilation" , "A tiny thing" , "Charged particle" , "Elementary particle with positive charge" , "Sub-atomic particle" .)