It swims with the current (8,3)
I believe the answer is:
electric eel
'it swims with' is the definition.
The definition suggests a singular noun which matches the answer.
'current' is the wordplay.
I cannot really see how this works, but
'current' could be 'electric' (synonyms) and 'electric' is found within the answer.
The remaining letters 'eel' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for electric eel that I've seen before include "Shocking fish" , "shocker" .)