Portray one patient for cosmetic treatment (5,3)

I believe the answer is:

paint job

'cosmetic treatment' is the definition.
(process of painting or re-painting something)

'portray one patient' is the wordplay.
'portray' becomes 'paint' (both can mean to depict in a particular way).
'one patient' becomes 'Job' (famously patient Old Testament figure).
'paint'+'job'='PAINT JOB'

'for' is the link.

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app