He calls for it in a flap, to save face (7)
I believe the answer is:
visitor
'he calls for it in a flap to save face' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he calls for' is the wordplay.
I cannot quite see how this works, but
'he' could be 'si' and 'si' is located in the answer.
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found in the answer.
The remaining letters 'vir' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for visitor that I've seen before include "Someone calling (again at 23?)" , "Person turning up" , "who might stay?" , "Caller, guest" , "One coming calling" .)