Forbidden to enter vaudeville gallery (7)
I believe the answer is:
illegal
'forbidden' is the definition.
(I've seen this before)
'enter vaudeville gallery' is the wordplay.
'enter' says the answer is hidden in the clue (I've seen 'entering' mean this).
'ILLEGAL' is hidden in the letters of 'vaudeville gallery'.
'to' acts as a link.
(Other definitions for illegal that I've seen before include "Not lawful" , "crooked" , "Wrong" , "Felonious" , "murder sure is!" .)