One who takes one may get it (4)
I believe the answer is:
life
'one' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for life that I've seen before include "Vitality, vigour" , "Animation" , "Birth to death" , "Existence - biography" , "and 12 Down: Biology, medicine, etc" .)