Quote:Can anyone give a fatwa?
No, should be someone who has studied extensively and has ejazah (a chain of teachers stretching back to the prophet (pbuh) himself).
Quote:A scholar? An iman?
Actually a better translation would be 'scientist', an Aalim is someone who has studied the Islamic Uloom (sciences). Obviously in the modern Western context, you'd not consider such a a translation accurate but that's actually the best translation. Also keep in mind that for most of Islamic history, there was no distinction between a scientist of the Islamic sciences and one of the natural sciences, most of the great scientists/scholars in Islam were also scientists/scholars in mathematics, astrology, geography etc.
By 'Iman' I think you mean Imam. Imam just means 'the guy at the front', coming from the Arabic word for forward/front Amaam, and it basically just means leader, usually leader of congregational prayers.
Quote:Is an iman considered to be "clergy"?
As stated already there's no concept of clergy in Islam, really.