Origins of torso?
I believe the answer is:
roots
'origins' is the definition.
('root' can be a synonym of 'origin')
'of torso?' is the wordplay.
'of' indicates an anagram (the answer comes from or 'of' the letters).
'torso' is an anagram of 'ROOTS'.
(Other definitions for roots that I've seen before include "Sources, rummages" , "Origins; cheers (for)" , "background" , "Cultural origin" , "Genealogy" .)