Family member with a right to be vague (7)
I believe the answer is:
unclear
'be vague' is the definition.
(similar in meaning)
'family member with a right' is the wordplay.
'family member' becomes 'uncle' (brother of a parent).
'with' says to put letters next to each other.
'a right' becomes 'ar' (I've seen this in other clues).
'uncle'+'ar'='UNCLEAR'
'to' acts as a link.
(Other definitions for unclear that I've seen before include "Not easy to see or understand" , "Cloudy or opaque" , "Vague" , "Not obvious, obscure" , "hard to understand" .)