Not a short way of saying "with one" (5)
I believe the answer is:
along
'with one' is the definition.
(I've seen this in another clue)
'not a short way of saying' is the wordplay.
I cannot really understand how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is located in the answer.
'a' is within the answer.
'way' could be 'n' (Compass direction - North) and 'n' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for along that I've seen before include "Forward - in a line" , "Sea monster, opposite Charybdis" , "Throughout; onward" , "Beside - as groups often sing!" , "By the side of" .)