Casts off, crossing river for scraps (6)
I believe the answer is:
shreds
'scraps' is the definition.
'casts off crossing river' is the wordplay.
'casts off' becomes 'sheds' ('shed' can be a synonym of 'cast off').
'crossing' is an insertion indicator.
'river' becomes 'r'.
'sheds' enclosing 'r' is 'SHREDS'.
'for' is the link.
(Other definitions for shreds that I've seen before include "Narrow strips cut or torn off" , "Rags, tattered pieces" , "Tears into small pieces" , "Tears into tiny pieces" , "Tears into strips" .)