One inquisitive policeman by corpse (8)
I believe the answer is:
Here is my best explanation:
'one inquisitive' is the definition.
(someone who is inquisitive)
'policeman by corpse' is the subsidiary indication.
'policeman' becomes 'busy' (informal UK term for a police officer).
'by' is a charade indicator (letters next to each other).
'corpse' becomes 'body' (I've seen this before).
(Other definitions for busybody that I've seen before include "butter in", "Prying person", "Meddlesome type", "A meddlesome interfering person", "Nosey Parker", "Proactive meddler", "Nosy Parker", "Person who meddles in the affairs of others", "Meddling person" and "he'll nose around".)