Quiet bachelor including wanderer's saying (7)
I believe the answer is:
proverb
'saying' is the definition.
(proverb is a kind of saying)
'quiet bachelor including wanderer's' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'including' indicates putting letters inside.
'wanderer' becomes 'rover' (synonyms).
'p'+'b'='pb'
'pb' enclosing 'rover' is 'PROVERB'.
(Other definitions for proverb that I've seen before include "Make haste slowly, perhaps" , "gnome" , "Saying encapsulating a general truth" , "Pithy saying expressing a general truth" , "Saying of great truth" .)