Related on the father's side (6)
I believe the answer is:
agnate
'related on the father's side' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for agnate that I've seen before include "Relative" , "Get an A (anag.)" , "Descended from the same male ancestor" , "Related through male descent on father's side (6)" .)