In the Euphrates, it can go by water (3)
I believe the answer is:
rat
'go by water' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'in the euphrates it' is the wordplay.
'in' says the answer is hidden in the clue.
'RAT' is hidden in the letters of 'euphrates it'.
'can' is the link.
Can you help me to learn more?
(Other definitions for rat that I've seen before include "Change sides" , "Treacherous person" , "Betray like a rodent" , "One deserting sinking ship" , "Despicable person" .)