Rubbish used to be tipped extensively, to begin with (5)
I believe the answer is:
waste
'rubbish' is the definition.
(thesaurus)
'used to be tipped extensively to begin with' is the wordplay.
'used to be' becomes 'was' (I've seen this before).
'to begin with' suggests taking the first letters.
The initial letters of 'tipped extensively' is 'te'.
'was'+'te'='WASTE'
(Other definitions for waste that I've seen before include "Refuse, garbage, rubbish" , "Use inefficiently or inappropriately" , "Uncultivated area" , "kill" , "Not use effectively" .)