Possible Clues:

• Primary source of income
• Basic meal
• Basic foods keep
• Primary source of income ... and words that can precede the two parts, respectively, of the answers to starred clues
• Means study in second-class state
• Means an unexciting sandwich
• Study in lodgings and say it's practical
• Urban trade debt ruined livelihood
• Ordinary components of pudding?
• Food largely prepared in guest house, say, is basically reliable