Not all there is to see in fourth rate feature (8)
I believe the answer is:
distrait
'not all there' is the definition.
(both can mean distracted)
'is to see in fourth rate feature' is the wordplay.
'to see in' means one lot of letters goes inside another.
'fourth rate' becomes 'd' (fourth best category after A, B and C).
'feature' becomes 'trait' (I've seen this before).
'd'+'trait'='dtrait'
'is' placed into 'dtrait' is 'DISTRAIT'.
(Other definitions for distrait that I've seen before include "Distraught in France" , "Being one [SCATTY]" , "Unable to concentrate for anxiety - it is trad (anag)" , "Preoccupied" , "Inattentive or absent-minded, from French" .)