Quietly, he occupies young relative (6)
I believe the answer is:
nephew
'relative' is the definition.
(nephew is a kind of relative)
'quietly he occupies young' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'occupies' indicates putting letters inside.
'young' becomes 'new' ('new' can be similar in meaning to 'young').
'p'+'he'='phe'
'phe' placed inside 'new' is 'NEPHEW'.
(Other definitions for nephew that I've seen before include "A sibling's child" , "Brother's/sister's son" , "Sibling's son" , "Male relative" , "Edward V to Richard III relation" .)