Wizardry of a long-distance runner on run not last! (4)
I believe the answer is:
mojo
'wizardry' is the definition.
(both can mean magic)
'a long-distance runner on run not last' is the wordplay.
'a long distance runner' becomes 'Mo' (Olympic runner Mo Farah).
'on' says to put letters next to each other.
'run' becomes 'jog' (jogging is a kind of running).
'not last' means to remove the last letter.
'jog' with its last letter taken off is 'jo'.
'mo'+'jo'='MOJO'
'of' is the link.
(Other definitions for mojo that I've seen before include "American charm" , "Magic charm or power in African-American culture, as heard in R&B music" , "Magical power" , "Magical influence" .)