Personal vessel among smarter yachts (6)
I believe the answer is:
artery
'personal vessel' is the definition.
(blood vessel within one's person)
'among smarter yachts' is the wordplay.
'among' indicates the answer is hidden within the clue.
'ARTERY' can be found hidden inside 'smarter yachts'.
(Other definitions for artery that I've seen before include "vital route" , "Felt amazement" , "Vital tube" , "bloody path" , "Important transport route" .)