Drink connection keeping pupils regularly missing (6)
I believe the answer is:
tipple
'drink' is the definition.
(tippling is a kind of drinking)
'connection keeping pupils regularly missing' is the wordplay.
'connection' becomes 'tie' (tie is a kind of connection).
'keeping' means one lot of letters goes inside another.
'regularly missing' means one should take alternating letters (letters removed at regular intervals).
The alternating letters of 'pupils' are 'ppl'.
'tie' placed around 'ppl' is 'TIPPLE'.
(Other definitions for tipple that I've seen before include "Paint < pot" , "fall" , "pint?" , "where coal is washed" , "Be in the habit of drinking" .)