Not speaking with relation? (3)
I believe the answer is:
mum
'relation?' is the definition.
(I know that mum subproperty of parent (unspecified))
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for mum that I've seen before include "Mother - she's the word for secrecy" , "Parent - shtoom" , "Silence" , "Keep quiet, mother" , "Silent; parent" .)