Family member with cataract, essentially it's foggy (7)
I believe the answer is:
unclear
'it's foggy' is the definition.
(thesaurus)
'family member with cataract essentially' is the wordplay.
'family member' becomes 'uncle' (brother of a parent).
'with' says to put letters next to each other.
'essentially' says to take the centre.
The middle of 'cataract' is 'ar'.
'uncle'+'ar'='UNCLEAR'
(Other definitions for unclear that I've seen before include "Not certain" , "Indistinct" , "Not apparent" , "Vague" , "An ulcer (anag)" .)