Clue: Temperance society conceals unopened wine vessel (5)
Answer: AORTA
Explanation: Definition: vessel
 AA(abbrev. for "Alcoholics Anonymous", a mutual aid society helping members recover from alcoholism by practising temperance/abstinence from alcohol) **containing**(conceals) "port"(a fortified wine) **minus its 1st letter**(unopened …).
Defn: A blood … in your body.