AJT, I didn't mean to question whether it's in your Chambers or not
(and I realise Chambers is the recommended reference), I was trying to say that I thought it could have been better clued, given that it doesn't appear in some dictionaries - the hefty Collins I use is normally very reliable. I also wonder whether ego meaning 'the I' (i.e. the sense of self), is the same as 'I', perhaps that seems a little nitpicky?
Here's the complete definition in Collins -
ego n., pl. egos. 1. the self of an individual person; the conscious subject. 2. Psycholanal. the conscious mind, based on perception of the environment from birth onwards; responsible for modifying the antisocial instincts of the id and itself modified by the conscience (superego). 3. one's image of oneself; morale: to boost one's ego. 4. egotism; conceit. [C19: from Latin: I]
Anyway, I'll try to remember it in future.