Mother's run? Not entirely (3)
I believe the answer is:
mar
'mother's run? not entirely' is the definition.
I can't tell whether this defines the answer.
'mother's run?' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'run?' becomes 'r' (cricket abbreviation).
'ma'+'r'='MAR'
Can you help me to learn more?
(Other definitions for mar that I've seen before include "Spoil or deface" , "Spoil stuff" , "Cause harm" , "Disfigure" , "wreck" .)