Stone me: man beheaded outside! (7)
I believe the answer is:
emerald
'stone' is the definition.
(type of gemstone)
'me man beheaded outside' is the wordplay.
I cannot quite see how this works, but
'me' is found in the answer.
'man' could be 'al' and 'al' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for emerald that I've seen before include "city in Oz?" , "Gem associated with Ireland" , "On of the Greens" , "Small size of type, in printing" , "La couleur" .)