Wobbly right, measure round waist (5)
I believe the answer is:
girth
'measure round waist' is the definition.
(girth can mean a measurement of someone's waist)
'wobbly right' is the wordplay.
'wobbly' indicates anagramming the letters (I've seen this in other clues).
'right' with letters rearranged gives 'GIRTH'.
(Other definitions for girth that I've seen before include "Distance round a body" , "A band passing under horse's belly" , "Distance around, often of the tummy" , "all the way round" , "Some tack" .)