Hangman perhaps dispatching old Punch (5)
I believe the answer is:
noser
'punch' is the definition.
(punch on the nose)
'hangman perhaps dispatching old' is the wordplay.
'hangman perhaps' becomes 'nooser' (someone who uses a noose).
'dispatching' is a deletion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'nooser' with 'o' taken away is 'NOSER'.
(Other definitions for noser that I've seen before include "curious one" , "busybody" , "Prying person" , "Severe rebuff" , "He's Snoopy" .)