Explorer's last seen on sledge with a pistol (5)
I believe the answer is:
luger
'a pistol' is the definition.
(I have seen 'German pistol' mean 'luger' so perhaps 'pistol' could also mean 'luger')
'explorer's last seen on sledge' is the wordplay.
'last' indicates one should take the final letters.
'seen on' is a charade indicator (letters next to each other).
'sledge' becomes 'luge' (I have seen 'Small sledge ' mean 'luge' so perhaps 'sledge' could also mean 'luge').
The final letter of 'explorer' is 'r'.
'r' after 'luge' is 'LUGER'.
'with' is the link.
(Other definitions for luger that I've seen before include "Shooter" , "Type of (German) automatic pistol" , "German semi-automatic pistol" , "Weapon" , "Make of pistol" .)