Waiter and cook to join firm, missing hotel opening (7)
I believe the answer is:
Here is my best explanation:
'waiter' is the definition.
(I've seen this before)
'cook to join firm missing hotel opening' is the subsidiary indication.
'cook' becomes 'stew' (stewing is a kind of cooking).
'to join' is a charade indicator (letters next to each other).
'firm missing hotel opening' becomes 'ard' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' is the link.
(Other definitions for steward that I've seen before include "Wed star (anag)", "Official at event", "Ship attendant", "Ship/aircraft attendant", "Cabin attendant", "Caretaker", "Administrator, manager, or waiter", "Airline host", "bailiff" and "race course official".)