Right to be uncommon (4)
I believe the answer is:
rare
'uncommon' is the definition.
(I know this)
'right to be' is the wordplay.
'right' becomes 'r' (common abbreviation).
'to be' becomes 'are' (I've seen this in another clue).
'r'+'are'='RARE'
(Other definitions for rare that I've seen before include "may be bloody" , "little done?" , "Still red inside (as hens' teeth?)" , "Singular, infrequent" , "Exceptionable" .)