Like mum, he always comes back (3)
I believe the answer is:
dad
'like mum he always comes back' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'like mum he' is the wordplay.
I cannot quite see how this works, but
'he' could be 'ad' and 'ad' is present in the answer.
A single letter 'd' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dad that I've seen before include "Mum's mate" , "Old man" , "Father, in short" , "Relation" , "Popular and informal father" .)