One boards alone travelling by air? (6)
I believe the answer is:
eolian
'air?' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'one boards alone travelling' is the wordplay.
'one' becomes 'i' (Roman numeral).
'boards' indicates putting letters inside.
'travelling' indicates anagramming the letters.
'alone' with letters rearranged gives 'eolan'.
'i' put within 'eolan' is 'EOLIAN'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for eolian that I've seen before include "type of harp" , "Wind-borne (Amer.)" .)