Second fool old leftie watched (9)
I believe the answer is:
monitored
'watched' is the definition.
The definition and answer can be both to do with perception as well as being past participle verbs.
Perhaps there's an association between them I don't understand?
'second fool old leftie' is the wordplay.
'second' becomes 'mo' (both are short periods of time).
'fool' becomes 'nit' (both can mean a stupid person).
'old' becomes 'o' (abbreviation).
'leftie' becomes 'red' (red can informally mean a political leftwinger).
'mo'+'nit'+'o'+'red'='MONITORED'
Can you help me to learn more?
(Other definitions for monitored that I've seen before include "Kept eye on" , "Watched carefully" , "Checked over time" .)