Gun right behind toboggan (5)
I believe the answer is:
luger
'gun' is the definition.
(type of pistol)
'right behind toboggan' is the wordplay.
'right' becomes 'r' (abbreviation).
'behind' is a charade indicator (letters next to each other).
'toboggan' becomes 'luge' (synonyms).
'r' put after 'luge' is 'LUGER'.
(Other definitions for luger that I've seen before include "Gun" , "She goes down rapidly" , "Make of pistol" , "German semi-automatic pistol" , "Shooter" .)