Gun - one found on a slippery slope (5)
I believe the answer is:
luger
'gun' is the definition.
(type of pistol)
'one found on a slippery slope' is the wordplay.
'one' becomes 'er' (I've seen this in other clues).
'found on' is a charade indicator (letters next to each other).
'a slippery slope' becomes 'lug' (I can't justify this - if you can you should give a lot more credence to this answer).
'er' put after 'lug' is 'LUGER'.
Can you help me to learn more?
(Other definitions for luger that I've seen before include "competes in winter Olympics?" , "Gun" , "Weapon" , "Type of (German) automatic pistol" , "German semi-automatic pistol" .)