Feel remorse, accepting regular income (7)
I believe the answer is:
revenue
'income' is the definition.
(revenue is a kind of income)
'feel remorse accepting regular' is the wordplay.
'feel remorse' becomes 'rue' (I've seen this before).
'accepting' means one lot of letters goes inside another.
'regular' becomes 'even' ('even' can be similar in meaning to 'regular').
'rue' going around 'even' is 'REVENUE'.
(Other definitions for revenue that I've seen before include "Money received" , "Takings" , "stream, perhaps" , "Ready" , "Gross business income" .)