One’s bust one’s hips (5,10)
I believe the answer is:
vital statistics
'hips' is the definition.
Both the definition and answer are plural nouns.
Perhaps you can see a link between them that I can't see?
'one's bust one's' is the wordplay.
I cannot really understand how this works, but
'one's' could be 'is' (Roman numeral) and 'is' is found within the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for vital statistics that I've seen before include "Miss World will have supplied?" , "Quantitative data" , "that are expanded by a corporation" , "Important figures" .)