... son cheer mother when father left (4,6)
I believe the answer is:
sole parent
'father left' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'son cheer mother' is the wordplay.
I cannot really understand how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is found in the answer.
'cheer' could be 'ole' (I've seen this in another clue) and 'ole' is found within the answer.
'mother' could be 'parent' (I've seen this in other clues) and 'parent' is located in the answer.
No letters remain.
This explanation may well be incorrect...
'when' acts as a link.
Can you help me to learn more?