Relative has a right to be rather vague (7)
I believe the answer is:
unclear
'rather vague' is the definition.
'unclear' can be an answer for 'vague' (similar in meaning). I am not certain of the 'rather' bit.
'relative has a right' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative).
'has' says to put letters next to each other.
'a right' becomes 'ar' (I've seen this in other clues).
'uncle'+'ar'='UNCLEAR'
'to be' is the link.
Can you help me to learn more?
(Other definitions for unclear that I've seen before include "hard to understand" , "Not apparent" , "An ulcer (anag)" , "Nebulous" , "Not transparent or intelligible" .)