Immovable (5)
'immovable' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for set that I've seen before include "Hard; place" , "number of games" , "become firm" , "Determined or congealed" , "Badger's burrow" .)
(Other definitions for stoic that I've seen before include "Zeno, say" , "not given to complaining" , "Solemn ceremony" , "One showing endurance during adversity" , "One who doesn't complain" .)