Organ in doll originally shaved off (4)
I believe the answer is:
indy
'organ' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I don't see?
'in doll originally shaved off' is the wordplay.
'originally' suggests taking the first letters.
'shaved off' becomes 'y' (I am not sure about this - if you are sure you should believe this answer much more).
The initial letter of 'doll' is 'd'.
'in'+'d'+'y'='INDY'
Can you help me to learn more?
(Other definitions for indy that I've seen before include "Form of competition between drivers" , "US motor-racing" , "US form of motor racing" , "Racing in fast cars" , "- - Car racing (in US)" .)