Various students turn up not serving alcohol (6)
I believe the answer is:
sundry
'various' is the definition.
(sundry means various or diverse)
'students turn up not serving alcohol' is the wordplay.
'students' becomes 'NUS' (National Union of Students).
'turn up' shows that the letters should be reversed in order.
'not serving alcohol' becomes 'dry' (dry can mean abstaining from drinking alcohol).
'nus' reversed gives 'sun'.
'sun'+'dry'='SUNDRY'
(Other definitions for sundry that I've seen before include "Assorted, miscellaneous" , "All and . . . . . . - various or several" , "Of various kinds" , "Several, separate, miscellaneous" , "All and . . . . . . includes everyone" .)