Possible Clues:

• Learnt one's own lessons, of course, by opening 18 across with dead cute cook
• Thought out loud following those opening 18 across and learnt one's own lessons, of course
• Did one's exercises on one's own at the start of 18 across - how informed is that?
• That is missing from 9 across as learned one wasn¿t taught a lesson!
• Like an autodidact
• Informed from a magazine?