Appointment without an opening at the time (5,4)
I believe the answer is:
blind date
'appointment' is the definition.
(blind date is a kind of appointment)
'without an opening at the time' is the wordplay.
'without an opening' becomes 'blind' (I am not sure about this - if you are sure you should believe this answer much more).
'at' says to put letters next to each other.
'the time' becomes 'date' (date is a kind of time).
'blind'+'date'='BLIND DATE'
Can you help me to learn more?
(Other definitions for blind date that I've seen before include "Social appointment with stranger" , "Romantic meeting with someone unknown" , "Romantic meeting between strangers?" , "Surprise assignation" , "Tryst with person unknown" .)