Goes on tablets, repeatedly consuming drink (7)
I believe the answer is:
elapses
'goes on' is the definition.
(elapsing is a kind of going on)
'tablets repeatedly consuming drink' is the wordplay.
'tablets' becomes 'es' (E can refer to an ecstasy tablet).
'repeatedly' shows that letters should be duplicated.
'consuming' indicates putting letters inside.
'drink' becomes 'lap' (lap can mean to drink).
'es' duplicated is 'eses'.
'eses' placed around 'lap' is 'ELAPSES'.
(Other definitions for elapses that I've seen before include "Slips away" , "Passes (in time)" .)