It's best worn above the waist (3)
I believe the answer is:
top
'it's best' is the definition.
(top can mean the very best)
'worn above the waist' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is present in the answer.
The remaining letters 'op' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for top that I've seen before include "premier" , "Zenith" , "Uppermost part" , "Highest point or position" , "jumper, say?" .)