Roots develop into a trunk (5)
I believe the answer is:
torso
'a trunk' is the definition.
(both can mean a person's chest)
'roots develop' is the wordplay.
'develop' indicates anagramming the letters.
'roots' with letters rearranged gives 'TORSO'.
'into' is the link.
(Other definitions for torso that I've seen before include "Trunk; headless, limbless body" , "Body without head, neck and limbs" , "Piece of bronze" , "Main part of human body" , "Body (excluding head, neck and limbs)" .)