Disgusting old boy with part in play (7)
I believe the answer is:
obscene
'disgusting' is the definition.
(obscene can mean disgusting or indecent)
'old boy with part in play' is the wordplay.
I cannot quite understand how this works, but
'old' could be 'o' (abbreviation) and 'o' is located in the answer.
'boy' could be 'b' (abbreviation used in schools) and 'b' is present in the answer.
'part' could be 'scene' (I have seen 'Part of play ' mean 'scene' so perhaps 'part' could also mean 'scene') and 'scene' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for obscene that I've seen before include "Repugnant; indecent" , "Indecent, lewd" , "Bawdy" , "offending sensibilities?" , "Dirty" .)