Frank is allowing access (4)
I believe the answer is:
open
I believe this clue is a double definition.
'frank' is the first definition.
(synonyms)
'allowing access' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for open that I've seen before include "Unrestricted; ready for business" , "golf contest" , "with no clear favourite" , "'Frank, not secret (4)'" , "Allowing entry and exit" .)