Leaders in very intense event compete (3)
I believe the answer is:
vie
'compete' is the definition.
(synonyms)
'leaders in very intense event' is the wordplay.
'leaders in' suggests taking the first letters.
The first letters of 'very intense event' is 'VIE'.
(Other definitions for vie that I've seen before include "Contend, compete" , "Eagerly compete" , "Contend for superiority" , "Engage in rivalry" , "Rival" .)