The cockney, more in need of cooling down, swims (5)
I believe the answer is:
otter
'down swims' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'the cockney more in need of cooling' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
'of' could be 'o' and 'o' is present in the answer.
The remaining letters 'ter' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for otter that I've seen before include "Fur possibly" , "Holt dweller" , "Water animal with webbed fee, brown fur and flat tail" , "River creature" , "furry creature" .)