Amateur in prison making way up (5)
I believe the answer is:
stair
'way up' is the definition.
(way to get upstairs)
'amateur in prison' is the wordplay.
'amateur' becomes 'a'.
'in' means one lot of letters goes inside another.
'prison' becomes 'stir' (informal term for prison).
'a' going into 'stir' is 'STAIR'.
'making' acts as a link.
(Other definitions for stair that I've seen before include "section of flight" , "One step of a flight" , "means to go down" , "Bit of a flight!" , "One of a flight of steps" .)