Vessel used in acupuncture (3)
I believe the answer is:
cup
'vessel' is the definition.
(cup is a type of vessel)
'in acupuncture' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CUP' is hidden in the letters of 'acupuncture'.
'used' is the link.
(Other definitions for cup that I've seen before include "Beaker" , "Sort of cake" , "Trophy; drinking vessel" , "Container to drink from - prize" , "Chalice; trophy" .)