By which to travel from Cairo? (3)
I believe the answer is:
air
'by which to travel' is the definition.
I can't tell whether this defines the answer.
'from cairo?' is the wordplay.
'from' says the answer is hidden in the clue.
'AIR' is hidden within 'cairo'.
Can you help me to learn more?
(Other definitions for air that I've seen before include "Atmosphere (of a melody?)" , "Carriage" , "what emerges from singer's lungs?" , "Divulge" , "Spread publicity" .)