Obsessive knight, socially acceptable, wearing blue? (8)
I believe the answer is:
neurotic
'obsessive' is the definition.
(similar in meaning)
'knight socially acceptable wearing blue?' is the wordplay.
'knight' becomes 'n' (chess).
'socially acceptable' becomes 'u'.
'wearing' is an insertion indicator.
'blue?' becomes 'erotic' (I've seen this before).
'u' going into 'erotic' is 'eurotic'.
'n'+'eurotic'='NEUROTIC'
(Other definitions for neurotic that I've seen before include "obsessive character" , "Very anxious and stressed" , "Emotionally disturbed" , "Paranoid" , "Over-anxious" .)