Fire and water? (4)
I believe the answer is:
burn
This clue is a double definition.
'fire' is the first definition.
(I know that fire can be written as burn)
'water?' is the second definition.
'and' is the link.
(Other definitions for burn that I've seen before include "Catch light; stream" , "Copy (a CD)" , "Scottish stream" , "Go up in flames; stream" , "Smart" .)