Author, one wunning along a wailway twack (5)
I believe the answer is:
twain
'author' is the definition.
(I've seen this before)
'one wunning along a wailway twack' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'a' could be 'an' and 'an' is found in the leftover letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for twain that I've seen before include "Mark in American literature" , "Mark ..... created Huckleberry Finn" , "Old pair beginning" , "Mark ___ , American writer" , "Two - Mark!" .)