On his own, Mr Sloan (3)
I believe the answer is:
tod
'his own mr sloan' is the definition.
The definition suggests a singular noun which matches the answer.
'on' is the wordplay.
I cannot quite understand how this works, but
'on' could be 'to' and 'to' is found in the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tod that I've seen before include "Former English weight for wool - dot it" , "One's alone on this" , "If you're on it, you're on your own" , "Fox" , "Sly person" .)