Oar scarcity upset the nobility (11)
I believe the answer is:
aristocracy
'the nobility' is the definition.
(synonyms)
'oar scarcity upset' is the wordplay.
'upset' indicates anagramming the letters.
'oar'+'scarcity'='oarscarcity'
'oarscarcity' with letters rearranged gives 'ARISTOCRACY'.
(Other definitions for aristocracy that I've seen before include "Upper classes" , "Upper class, nobility" , "Privileged class" , "Noble class" , "those born ahead of others?" .)