So superior, yet of little cash value (3)
I believe the answer is:
sou
'of little cash value' is the definition.
The definition suggests a singular noun which matches the answer.
'so superior' is the wordplay.
'superior' becomes 'U' (U can mean upper-class, as in U and non-U speech).
'so'+'u'='SOU'
'yet' acts as a link.
Can you help me to learn more?
(Other definitions for sou that I've seen before include "Little money once" , "Something of little worth" , "almost worthless" , "Defunct French coin" , "16 French coin" .)