Key at home in receptacle (3)
I believe the answer is:
bin
'receptacle' is the definition.
(I've seen this before)
'key at home' is the wordplay.
'key' becomes 'b' (eg B major, musical key).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'b'+'in'='BIN'
'in' acts as a link.
(Other definitions for bin that I've seen before include "Storage receptacle" , "Domestic receptacle for rubbish" , "Common receptacle for household waste" , "Household rubbish is placed in it" , "Storage container" .)