Box of vital parts? (5)
I believe the answer is:
trunk
'box' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for trunk that I've seen before include "Baggage item" , "Main stem of tree" , "Elephant's nose" , "Large luggage case" , "Part of a tree - part of an elephant" .)