Scottish poet avoiding southern stream (4)
I believe the answer is:
burn
'stream' is the definition.
(a burn is a small stream)
'scottish poet avoiding southern' is the wordplay.
'scottish poet' becomes 'Burns' (Robert Burns).
'avoiding' indicates named letters should be taken away.
'southern' becomes 's' (abbreviation).
'burns' with 's' taken out is 'BURN'.
(Other definitions for burn that I've seen before include "Go up in smoke" , "Char" , "Catch light; stream" , "northern stream" , "Scottish stream" .)