Old boys better out of sight (8)
I believe the answer is:
obscured
'out of sight' is the definition.
(I've seen this before)
'old boys better' is the wordplay.
'old boys' becomes 'OBs' (OB is short for old boy).
'better' becomes 'cured' (after being sick).
'obs'+'cured'='OBSCURED'
(Other definitions for obscured that I've seen before include "Good news from clinic about schoolboy no longer" , "unnoticed" , "Overshadowed or eclipsed" , "Hid from view" , "Concealed from view, made indistinct" .)