Administer an oath to (5,2)
'administer an oath to' is the definition.
(synonyms)
This is all the clue.
(Other definitions for swear in that I've seen before include "Inaugurate by oath" , "Admit to office" , "Administer oath to one taking up office" , "prepare to deliver evidence" , "bring candidate to office" .)
'administer an oath to' is the definition.
(synonyms)
This is all the clue.