Cases in silence put into toboggan (7)
I believe the answer is:
luggage
'cases' is the definition.
(I've seen this before)
'silence put into toboggan' is the wordplay.
'silence' becomes 'gag' (gagging is a kind of silencing).
'put into' means one lot of letters goes inside another.
'toboggan' becomes 'luge' (synonyms).
'gag' put inside 'luge' is 'LUGGAGE'.
'in' acts as a link.
(Other definitions for luggage that I've seen before include "gear carried" , "Traveller's bags etc" , "Bags and baggage" , "case?" , "Travelling bags etc." .)