It's obvious to a quiet mother or father (8)
I believe the answer is:
apparent
'it's obvious' is the definition.
(similar in meaning)
'a quiet mother or father' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'mother or father' becomes 'parent' (I've seen this in another clue).
'a'+'p'+'parent'='APPARENT'
'to' is the link.
(Other definitions for apparent that I've seen before include "readily understood" , "Ostensible, seeming" , "Pane part may be quite obvious" , "Writ large" , "Visible - plain - presumable" .)