Go up stream (4)
I believe the answer is:
burn
This clue could be a double definition.
'go up' is the first definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
'stream' is the second definition.
(a burn is a small stream)
Can you help me to learn more?
(Other definitions for burn that I've seen before include "northern stream" , "Catch light; stream" , "Set 1 across [ALIGHT]" , "Incinerate" , "Smart" .)