Loss of it can be humiliating (4)
I believe the answer is:
face
This clue might be a double definition.
'loss' is the first definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'it can be humiliating' is the second definition.
The definition suggests a singular noun which matches the answer.
'of' is the link.
Can you help me to learn more?
(Other definitions for face that I've seen before include "Watch's dial" , "set of features" , "Outward appearance" , "Countenance, visage" , "Cope with" .)