Relative amicability rules, initially? It's not obvious (7)
I believe the answer is:
unclear
'not obvious' is the definition.
(I've seen this before)
'relative amicability rules initially?' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative**).
'initially?' suggests taking the first letters (I've seen 'initially' mean this).
The initial letters of 'amicability rules' is 'ar'.
'uncle'+'ar'='UNCLEAR'
'it's' is the link.
(Other definitions for unclear that I've seen before include "Not easy to grasp" , "Indistinct" , "Poorly described" , "An ulcer (anag)" , "Not easy to see or understand" .)