The brother of one’s parent (5)
I believe the answer is:
uncle
'the brother of one's parent' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for uncle that I've seen before include "Male family member" , "Brother of one's parent" , "older relative" , "Pawnbroker's nickname" , ". . . . . Sam, the US government" .)