Different temperature for Henry's swimmer (5)
I believe the answer is:
otter
'swimmer' is the definition.
(I have seen 'Good swimmer' mean 'otter' so perhaps 'swimmer' could also mean 'otter')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for otter that I've seen before include "Fish-eater of the weasel family" , "Aquatic river mammal" , "Water creature" , "river in Honiton" , "one that eats fish" .)