Clutching a small volume, chairman turns philosopher (5)
I believe the answer is:
occam
'philosopher' is the definition.
(I know that Occam is a philosopher)
'clutching a small volume chairman turns' is the wordplay.
'clutching' is an insertion indicator.
'a small volume' becomes 'cc' (cubic centimetre).
'chairman' becomes 'Mao' (Chinese leader Chairman Mao).
'turns' says the letters should be written backwards.
'cc' put within 'mao' is 'macco'.
'macco' reversed gives 'OCCAM'.
(Other definitions for occam that I've seen before include "One scientific principle is -'s razor" , "English philosopher, William (with a Razor!), d. 1349" , "medieval philosopher" , "___ 's razor - computer programming language" , "Man with razor" .)