Channel or river filled with fish? On the contrary (6)
I believe the answer is:
trench
'channel' is the definition.
(I've seen this before)
'river filled with fish? on the contrary' is the wordplay.
I cannot quite see how this works, but
'river' could be 'r' (abbreviation for river) and 'r' is located in the answer.
'fish?' could be 'tench' (tench is a kind of fish) and 'tench' is found in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
'or' acts as a link.
Can you help me to learn more?
(Other definitions for trench that I've seen before include "A military ditch for soldiers" , "Cutting" , "Ditch, as a fortification say" , "It may be slit" , "deep channel" .)