Predatory river fish (4)
I believe the answer is:
pike
This clue could be a double definition.
'predatory river' is the first definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'fish' is the second definition.
(pike is a kind of fish)
Can you help me to learn more?
(Other definitions for pike that I've seen before include "Predator with strong teeth" , "Fish - medieval weapon" , "Long European freshwater predator" , "Predatory freshwater fish" , "Weapon on long shaft; Northern hill" .)