Reserve right in company for a philosopher (6)
I believe the answer is:
cicero
'a philosopher' is the definition.
(I know this)
'reserve right in company' is the wordplay.
'reserve' becomes 'ice' (both can mean aloofness).
'right' becomes 'r' (common abbreviation).
'in' indicates putting letters inside.
'company' becomes 'co' (abbreviation).
'ice'+'r'='icer'
'icer' going into 'co' is 'CICERO'.
'for' acts as a link.
(Other definitions for cicero that I've seen before include "One-time consul" , "Old Roman statesman and orator" , "Roman orator; type size above pica" , "Orator's" , "wartime spy" .)