Sort of seat to contest? (3)
I believe the answer is:
box
This clue is a double definition.
'sort of seat' is the first definition.
'contest?' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for box that I've seen before include "Receptacle" , "Present container?" , "Spar; container" , "Wooden case" , "Carton" .)