Extract idiot blocking attendant (7)
I believe the answer is:
'extract' is the definition.
(I have seen 'Literary extract' mean 'passage' so perhaps 'extract' could also mean 'passage')
'idiot blocking attendant' is the wordplay.
'idiot' becomes 'ass' (I've seen this in another clue).
'blocking' means one lot of letters goes inside another.
'attendant' becomes 'page' (page is a kind of attendant).
'ass' going inside 'page' is 'PASSAGE'.
(Other definitions for passage that I've seen before include "Alley - corridor" , "equestrian manoeuvre" , "Short section of text" , "Section of text; journey" , "Section of musical or literary work" .)