Briton went off out in order to process raw fish (7,5)
I believe the answer is:
rainbow trout
'fish' is the definition.
(I know that rainbow trout is a type of trout)
'briton went off out in order to process raw' is the wordplay.
I cannot really see how this works, but
'off' could be 'out' (both can mean wrong or inaccurate) and 'out' is found within the answer.
'in' is within the answer.
'order' could be 'o' (abbreviation e.g. in British honours OM, OBE etc.) and 'o' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rainbow trout that I've seen before include "Popular food fish" , "Finely coloured fish" , "game swimmer" .)