Spacious quality in Romeo’s pants ultimately disappoints (9)
I believe the answer is:
roominess
'spacious quality' is the definition.
The definition and answer can be both human attributes as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'in romeo's pants ultimately disappoints' is the wordplay.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'ultimately' suggests the final letters.
The final letter of 'disappoints' is 's'.
'in'+'romeos'='inromeos'
'inromeos' is an anagram of 'roomines'.
'roomines'+'s'='ROOMINESS'
Can you help me to learn more?
(Other definitions for roominess that I've seen before include "near-emptyness of space" , "Capaciousness" .)