Protracted answer leads to a more advanced state (5)
I believe the answer is:
along
'to a more advanced state' is the definition.
I can't tell whether this definition defines the answer.
'protracted answer leads' is the wordplay.
'protracted' becomes 'long' (similar in meaning).
'answer' becomes 'a' (abbreviation eg in Q and A).
'leads' says to put letters next to each other (some letters go in front of others).
'long' put after 'a' is 'ALONG'.
Can you help me to learn more?
(Other definitions for along that I've seen before include "Forward - in a line" , "Lengthwise" , "Throughout; onward" , "Beside - as groups often sing!" , "By the side of" .)