A drink on the side (4)
I believe the answer is:
port
I believe this is a double definition.
'a drink' is the first definition.
(port is a kind of drink)
'the side' is the second definition.
(port is a kind of side)
'on' is the link.
(Other definitions for port that I've seen before include "Light enough to carry" , "Sweet dark red fortified wine taken after meal" , "After-dinner wine" , "Drink passed to the left" , "Ship's left - Dover, perhaps" .)