Old building material containing rubbish tip waste (9)

'waste' is the definition.
(I know that excrement is a type of waste)

'old building material containing rubbish tip' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'building material' becomes 'cement' (cement is a kind of building material).
'containing' means one lot of letters goes inside another.
'tip' suggests taking the first letters (I've seen 'tips' mean this (tip can refer to the top end of something)).
The initial letter of 'rubbish' is 'r'.
'cement' placed around 'r' is 'crement'.
'ex'+'crement'='EXCREMENT'