He's calling the dog McNeill (8)
I believe the answer is:
whistler
'he's calling the dog mcneill' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he's calling the' is the wordplay.
I cannot quite understand how this works, but
'he's' could be 'his' and 'his' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for whistler that I've seen before include "English painter or mouth musician" , "Olympic ski resort" , "pretending to be brave in the dark?" , "referee" , "American artist who painted his mother, d. 1903" .)