Curse West Country river case (8)
I believe the answer is:
execrate
'curse' is the definition.
(I've seen this before)
'west country river case' is the wordplay.
'west country river' becomes 'exe' (I've seen this before).
'case' becomes 'crate' (crating is a kind of casing).
'exe'+'crate'='EXECRATE'
(Other definitions for execrate that I've seen before include "Express great loathing for" , "Harshly criticise" , "'Abhor, find repugnant (8)'" , "Feel great loathing for" , "Loudly disapprove" .)