It's best worn on the upper body (3)
I believe the answer is:
top
'it's best' is the definition.
(top can mean the very best)
'worn on the upper body' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
The remaining letters 'op' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for top that I've seen before include "Pinnacle" , "Better" , "Summit or spinning toy" , "Highest point or position" , "Best" .)