Drink Tango, following code (4)
I believe the answer is:
pint
'drink' is the definition.
(pint is a unit of liquid volume)
'tango following code' is the wordplay.
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'following' means one lot of letters go next to another.
'code' becomes 'pin' (a PIN number is a 4-digit code).
't' after 'pin' is 'PINT'.
(Other definitions for pint that I've seen before include "small amount" , "Half a quart" , "One eighth of a gallon" , "Unit of beer" , "Quantity" .)