Opinion from family enveloped in obsession (8)
I believe the answer is:
thinking
'opinion' is the definition.
(thesaurus)
'family enveloped in obsession' is the wordplay.
'family' becomes 'kin' ('kin' can be a synonym of 'family').
'enveloped in' is an insertion indicator.
'obsession' becomes 'thing' (I've seen this before).
'kin' inserted inside 'thing' is 'THINKING'.
'from' acts as a link.
(Other definitions for thinking that I've seen before include "Rational" , "Thought" , "Cogitating" , "Pondering" , "giving opinion" .)