Burn coming from ocean before river (4)
I believe the answer is:
sear
'burn' is the definition.
(sear can mean to burn)
'ocean before river' is the wordplay.
'ocean' becomes 'sea' (synonyms).
'before' is a charade indicator (letters next to each other).
'river' becomes 'r' (abbreviation for river).
'sea'+'r'='SEAR'
'coming from' acts as a link.
(Other definitions for sear that I've seen before include "Burn, scorch intensely" , "Dried-up, parched" , "Cook (quickly at great heat)" , "Withered" , "Cauterize" .)