Waist measurement potentially right (5)
I believe the answer is:
girth
'waist measurement' is the definition.
(I've seen this before)
'potentially right' is the wordplay.
'potentially' indicates an anagram (letters have the potential to spell a new word).
'right' anagrammed gives 'GIRTH'.
(Other definitions for girth that I've seen before include "all the way round" , "Some tack" , "The distance around a thing or tummy" , "A band passing under horse's belly" , "Size of waist perhaps" .)