Stick up around a level entrance (4)
I believe the answer is:
door
'entrance' is the definition.
(I know that door is a type of entrance)
'stick up around a level' is the wordplay.
'stick up' becomes 'dor' (I can't explain this - if you can you should believe this answer much more).
'around' means one lot of letters goes inside another.
'a level' becomes 'O' (O level is an example).
'dor' placed around 'o' is 'DOOR'.
Can you help me to learn more?
(Other definitions for door that I've seen before include "Entry point" , "Alternative to knocker" , "Hinged barrier" , "Opener" , "Barrier to open and close" .)