A male child of one’s child (8)
I believe the answer is:
grandson
'a male child of one's child' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for grandson that I've seen before include "Dons rang (anag) - relative" , "Male descendent" , "Young male relative" , "Younger male relative" , "Junior relative" .)