Boasts of five of parents’ siblings (6)
I believe the answer is:
vaunts
'boasts of' is the definition.
(I've seen this in another clue)
'five of parents' siblings' is the wordplay.
I cannot really understand how this works, but
'five' could be 'v' (Roman numeral) and 'v' is located in the answer.
The remaining letters 'aunts' is a valid word which might be clued in a way I don't understand.
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" .)