Poseur failing to hide, for example, unconscious inhibitor (8)
I believe the answer is:
superego
'unconscious inhibitor' is the definition.
(part of the unconscious inhibiting behaviour)
'poseur failing to hide for example' is the wordplay.
'failing' is an anagram indicator.
'to hide' means one lot of letters goes inside another.
'for example' becomes 'eg' (synonyms).
'poseur' anagrammed gives 'supero'.
'supero' placed around 'eg' is 'SUPEREGO'.
(Other definitions for superego that I've seen before include "makes one feel guilty" , "Conscience, perhaps" , "piece of his mind?" , "Freud's part of the mind that acts as a self-critical conscience" , "Internal monitor of psyche" .)