Complaint raised about Democratic Attorney-General’s source of eats (7)

'eats' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

'complaint raised about democratic attorney-general's source' is the wordplay.
'complaint' becomes 'beef' (beef can mean a complaint or objection).
'raised' shows that the letters should be reversed in order (going up in a down clue).
'about' is an insertion indicator.
'democratic' becomes 'd' (political abbreviation).
'source' indicates taking the first letters (source can mean a beginning or origin).
The first letters of 'attorney general' is 'ag'.
'beef' written backwards gives 'feeb'.
'feeb' placed around 'd' is 'feedb'.
'feedb'+'ag'='FEEDBAG'

'of' is the link.

Can you help me to learn more?