Vessel used in acupuncture (3)
I believe the answer is:
cup
'vessel' is the definition.
(I've seen this in other clues)
'in acupuncture' is the wordplay.
'in' indicates a hidden word.
'CUP' is hidden in the letters of 'acupuncture'.
'used' acts as a 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" .)