Mostly calm, appeal with resigned expression (2,2,2)
I believe the answer is:
so be it
'mostly calm' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'appeal with resigned expression' is the wordplay.
I cannot quite see how this works, but
'appeal' could be 'it' and 'it' is present in the answer.
'expression' could be 'sob' (I have seen 'Expression of distress' mean 'sob' so perhaps 'expression' could also mean 'sob') and 'sob' is present in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for so be it that I've seen before include "form of acceptance" , "Oh, OK then" .)