He doesn't like to assume anything (6)
I believe the answer is:
nudist
'he doesn't like to assume anything' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
This is all the clue.
Can you help me to learn more?
(Other definitions for nudist that I've seen before include "I lead a bare existence" , "Streaker?" , "exhibitionist" , "Person who discards clothes out of conviction" , "One going naked" .)