Hidden from view, old boy's pickled (8)
I believe the answer is:
obscured
'hidden from view' is the definition.
'old boy's pickled' is the wordplay.
'old boy's' becomes 'OBs' (abbreviation for a private school 'old boy').
'pickled' becomes 'cured' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'obs'+'cured'='OBSCURED'
Can you help me to learn more?
(Other definitions for obscured that I've seen before include "Veiled, hidden" , "Concealed from view, made indistinct" , "unnoticed" , "Hid from view" , "kept out of sight" .)