Guard denied special access (5)
I believe the answer is:
entry
'access' is the definition.
(I know that entry is a type of access)
'guard denied special' is the wordplay.
'guard' becomes 'sentry' (sentry is a kind of guard).
'denied' is a deletion indicator (the word is denied or deprived of certain letters).
'special' becomes 'S' (common abbreviation as in Special Air Service).
'sentry' with 's' removed is 'ENTRY'.
(Other definitions for entry that I've seen before include "Record - number of contestants" , "Competitors - way in" , "Doorway" , "Door, access" , "Lobby" .)