Material upsetting - issue about one coming out (9)

'out' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'material upsetting issue about one' is the wordplay.
'material' becomes 'serge' (serge is a kind of material).
'upsetting' says the letters should be written in reverse.
'issue' becomes 'son' (issue can mean someone's offspring).
'about' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'serge' in reverse letter order is 'egres'.
'son' enclosing 'i' is 'sion'.
'egres'+'sion'='EGRESSION'

'coming' is the link.

Can you help me to learn more?