Before noon permit is open (8)
I believe the answer is:
amenable
'is open' is the definition.
(I've seen this before)
'before noon permit' is the wordplay.
'before noon' becomes 'am' (as in AM on a clock).
'permit' becomes 'enable' (I've seen this in another clue).
'am'+'enable'='AMENABLE'
(Other definitions for amenable that I've seen before include "Flexible, agreeable" , "Nameable as being willing to be controlled" , "Agreeable and accommodating" , "Friendly" , "Compliant - persuadable" .)