Boasts of relatives running after first victory (6)
I believe the answer is:
vaunts
'boasts of' is the definition.
(I've seen this in another clue)
'relatives running after first victory' is the wordplay.
I cannot really understand how this works, but
'relatives' could be 'aunts' (aunt is a kind of relative) and 'aunts' is found in the answer.
'victory' could be 'v' and 'v' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for vaunts that I've seen before include "Boasts, brags" , "Shows off" .)