Former pupil to see lot turning outdated (8)
I believe the answer is:
obsolete
'outdated' is the definition.
(synonyms)
'former pupil to see lot turning' is the wordplay.
'former pupil' becomes 'OB' (abbreviation for 'Old Boy').
'to' means one lot of letters go next to another.
'turning' indicates anagramming the letters.
'see'+'lot'='seelot'
'seelot' anagrammed gives 'solete'.
'ob'+'solete'='OBSOLETE'
(Other definitions for obsolete that I've seen before include "No longer current" , "'No longer used, out of date (8)'" , "Obese lot may be out of date" , "Antiquated" , "No longer useful" .)