So a motherless man has a relationship (3)
I believe the answer is:
son
'a relationship' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'so a motherless man' is the wordplay.
'a motherless man' becomes 'n' (knight, a man in chess. I am not sure about the 'motherless' bit.**).
'so'+'n'='SON'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for son that I've seen before include "Male descendant" , "A relative" , "Human offspring" , "Express paper" , "Male offspring" .)