Disorder starts to put stress on Irish rising in pleasant place (9)

'disorder' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?

'starts to put stress on irish rising in pleasant place' is the wordplay.
'starts to' suggests taking the first letters.
'irish' becomes 'IR' (abbreviation).
'rising' says the letters should be written in reverse (letters written upwards in a down clue).
'in pleasant place' becomes 'asis' (I can't explain this - if you can you should give a lot more credence to this answer).
The first letters of 'put stress on' is 'pso'.
'ir' back-to-front is 'ri'.
'pso'+'ri'+'asis'='PSORIASIS'

Can you help me to learn more?