Trunk's one end of elephant, roughly (5)
I believe the answer is:
'trunk's' is the definition.
('torso' can be a synonym of 'trunk')
'one end of elephant roughly' is the wordplay.
'one end of' suggests the final letters.
'roughly' becomes 'orso' ('or so' can be a synonym of 'roughly').
The final letter of 'elephant' is 't'.
(Other definitions for torso that I've seen before include "part of body will be found" , "Trunk of human body" , "Roots out in trunk of the body" , "Chest" , "Trunk; headless, limbless body" .)