Refuse when beginning to recycle to break bed down (5)
I believe the answer is:
dross
'refuse' is the definition.
(thesaurus)
'beginning to recycle to break bed down' is the wordplay.
'beginning to' indicates taking the first letters.
'to break' indicates putting letters inside.
'bed down' becomes 'doss' (dossing is a kind of bedding down).
The first letter of 'recycle' is 'r'.
'r' inserted within 'doss' is 'DROSS'.
'when' acts as a link.
(Other definitions for dross that I've seen before include "Rubbish; impurities" , "Worthless matter" , "Impurity" , "Worthless stuff" , "Waste matter, refuse" .)