Old philosopher stops gathering old information (8)
I believe the answer is:
diogenes
'old philosopher' is the definition.
(ancient Greek philosopher)
'stops gathering old information' is the wordplay.
'stops' becomes 'dies' (as in a machine stopping or dying).
'gathering' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'information' becomes 'gen' (gen can informally mean information).
'o'+'gen'='ogen'
'dies' going around 'ogen' is 'DIOGENES'.
(Other definitions for diogenes that I've seen before include "Athenian philosopher who lived in a tub" , "Philosophical fellow" , "Greek cynic philosopher who lived in tub" .)