Income source opening as dole is replaced (3,3,7)
I believe the answer is:
old age pension
'income source' is the definition.
(source of income for pensioners)
'opening as dole is replaced' is the wordplay.
'is replaced' is an anagram indicator.
'opening'+'as'+'dole'='openingasdole'
'openingasdole' anagrammed gives 'OLD-AGE PENSION'.
(Other definitions for old age pension that I've seen before include "Senior citizen's allowance" , "Source of income" .)