Disgusting old book and part of play (7)
I believe the answer is:
obscene
'disgusting' is the definition.
(obscene can mean disgusting or indecent)
'old book and part of play' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'book' becomes 'b' (abbreviation for book).
'and' is a charade indicator (letters next to each other).
'part of play' becomes 'scene' ('scene' is part of 'play').
'o'+'b'+'scene'='OBSCENE'
(Other definitions for obscene that I've seen before include "Bawdy" , "Disgusting, repugnant" , "Shocking" , "offending sensibilities?" , "X-rated" .)