Maybe Trent Alexander-Arnold finally leaving club (5)
I believe the answer is:
river
'club' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for river that I've seen before include "One splits" , "It flows" , "Eg, Trent" , "Thames is one" , "Tees, perhaps" .)