Hollow container by river (6)
I believe the answer is:
crater
'hollow' is the definition.
(thesaurus)
'container by river' is the wordplay.
'container' becomes 'crate' (crate is a kind of container).
'by river' becomes 'r' (I am not sure about the 'by' bit.**).
'crate'+'r'='CRATER'
(Other definitions for crater that I've seen before include "Great hole as on top of volcano" , "Hole formed by impact or explosion" , "Geological depression" , "Bowl-shaped cavity, in a volcano say" , "Bowl-shaped cavity as on volcano peak" .)