...ergo sum initially includes case for philosopher (8)
I believe the answer is:
socrates
'philosopher' is the definition.
(Socrates is an example)
'ergo sum initially includes case' is the wordplay.
'ergo' becomes 'so' ('so' can be a synonym of 'ergo').
'initially' indicates taking the first letters.
'includes' indicates putting letters inside.
'case' becomes 'crate' (I've seen this before**).
The initial letter of 'sum' is 's'.
'so'+'s'='sos'
'sos' enclosing 'crate' is 'SOCRATES'.
'for' acts as a link.
(Other definitions for socrates that I've seen before include "Coarsest one of great Greek philosophers" , "Wise guy" , "sage from Greece" , "Deep thinker" , "old question-master?" .)