... to take in a Chinese philosophy (3)
I believe the answer is:
tao
'chinese philosophy' is the definition.
(I've seen this in another clue)
'to take in a' is the wordplay.
'take in' indicates putting letters inside.
'to' enclosing 'a' is 'TAO'.
(Other definitions for tao that I've seen before include "Chinese philosophical principle" , "Confucian way to be followed" , "Universal principle of Chinese philosophy" , "true path" , "Philosophical principle, the way" .)