Tycoon, not married, is related in father's side (6)
I believe the answer is:
agnate
'related in father's side' is the definition.
'agnate' can be an answer for 'related' (I've seen this before). I am unsure of the 'in father's side' bit.
'tycoon not married' is the wordplay.
'tycoon' becomes 'magnate' (synonyms).
'not' suggests deleting specific letters.
'married' becomes 'm'.
'magnate' with 'm' taken out is 'AGNATE'.
'is' is the link.
Can you help me to learn more?
(Other definitions for agnate that I've seen before include "Descended from the same male ancestor" , "Get an A (anag.)" , "Related through male descent on father's side (6)" , "Relative" .)