Bung very quietly into store, perhaps (7)
I believe the answer is:
stopper
'bung' is the definition.
(thesaurus)
'very quietly into store perhaps' is the wordplay.
'very quietly' becomes 'pp'.
'into' means one lot of letters goes inside another.
'perhaps' is an anagram indicator.
'store' is an anagram of 'stoer'.
'pp' put into 'stoer' is 'STOPPER'.
(Other definitions for stopper that I've seen before include "Plug for a bottle" , "One blocks" , "Plug - cork" , "Bung" , "Perhaps cork" .)