Body temperature (approx.) (5)
I believe the answer is:
torso
'body' is the definition.
(a person's middle)
'temperature approx' is the wordplay.
'temperature' becomes 't' (abbreviation).
'approx' becomes 'orso' (I can't justify this - if you can you should believe this answer much more).
't'+'orso'='TORSO'
Can you help me to learn more?
(Other definitions for torso that I've seen before include "Trunk of human body" , "Trunk, something unfinished" , "Body's core" , "part of body will be found" , "Body (excluding head, neck and limbs)" .)