Leave a drink without potassium (4)
I believe the answer is:
skip
'leave' is the definition.
(I know that leave is the is a more specific form of the action of skip.)
'a drink without potassium' is the wordplay.
'a drink' becomes 'sip' (I've seen this in another clue).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'potassium' becomes 'K' (K is the chemical symbol for potassium).
'sip' enclosing 'k' is 'SKIP'.
(Other definitions for skip that I've seen before include "Omit - jump over rope" , "Omit; fail to attend" , "leading curler" , "leave something out" , "Bob" .)