Perceptive faculty this person mentions audibly (8)
I believe the answer is:
'perceptive faculty' is the definition.
(I've seen this before)
'this person mentions audibly' is the wordplay.
'this person' becomes 'I'.
'mentions' shows a homophone (sound like) (I've seen 'mentioned' mean this).
'audibly' becomes 'sight' (I am not sure about this - if you are sure you should believe this answer much more).
'i' sounds like 'eye'.
(Other definitions for eyesight that I've seen before include "Yes, eight required for vision" , "perception" , "Purpose of certain organs" , "Seeing ability" , "Seeing faculty" .)