Nattering about Cairo, excitedly, as a place they have not yet explored (5,9)
I believe the answer is:
terra incognita
'a place they have not yet explored' is the definition.
The definition suggests an adverb but the answer is not.
'nattering about cairo excitedly' is the wordplay.
'about' is a charade indicator (letters next to each other).
'excitedly' is an anagram indicator (letters excited or stimulated into a new form).
'nattering' after 'cairo' is 'caironattering'.
'caironattering' anagrammed gives 'TERRA INCOGNITA'.
'as' acts as a link.
Can you help me to learn more?
(Other definitions for terra incognita that I've seen before include "abode of monsters once - with 17d" , "unsurveyed land" , "Unknown territory" , "country that's never been surveyed" , "riots in strange land" .)