Leave in the morning quietly after month (6)
I believe the answer is:
decamp
'leave' is the definition.
(decamping is a kind of leaving)
'morning quietly after month' is the wordplay.
'morning' becomes 'am'.
'quietly' becomes 'p' (p for piano and quiet).
'after' says to put letters next to each other.
'month' becomes 'dec' (Dec is an example).
'am'+'p'='amp'
'amp' after 'dec' is 'DECAMP'.
'in the' is the link.
(Other definitions for decamp that I've seen before include "Split" , "Make sudden breakaway" , "Run away (from responsibility)" , "Fold up tents and depart" , "Bolt" .)