Not the obvious way you progress initially into historic city (6)
I believe the answer is:
bypath
'not the obvious way' is the definition.
I can't judge whether this defines the answer.
'you progress initially into historic city' is the wordplay.
'initially' indicates taking the first letters.
'into' means one lot of letters goes inside another.
'historic city' becomes 'bath' (English city. I am not sure about the 'historic' bit.).
The first letters of 'you progress' is 'yp'.
'yp' going within 'bath' is 'BYPATH'.
Can you help me to learn more?
(Other definitions for bypath that I've seen before include "Minor route" , "Secluded way" .)