Kills a doctor and confesses (6)
I believe the answer is:
drowns
'kills' is the definition.
(drowning is a kind of killing)
'a doctor and confesses' is the wordplay.
'a doctor' becomes 'Dr' (abbreviation).
'and' means one lot of letters go next to another.
'confesses' becomes 'owns' (I've seen this before).
'dr'+'owns'='DROWNS'
(Other definitions for drowns that I've seen before include "Dies by submersion in water" , "Suffocates in water" , "Goes under" , "Kills in water or overpowers sound" , "Submerges" .)