After beheading handle slippery thing (3)
I believe the answer is:
eel
'slippery thing' is the definition.
(eel can mean a slippery person)
'after beheading handle' is the wordplay.
'after beheading' means to remove the first letter.
'handle' becomes 'feel' (I've seen this in another clue).
'feel' with its initial letter taken off is 'EEL'.
(Other definitions for eel that I've seen before include "Teleost fish" , "Slippery creature" , "Proverbially slippery fish" , "Slippery swimmer (may be jellied)" , "Snaky fish" .)