Swear word used in set-to at hotel (4)
I believe the answer is:
oath
'swear word' is the definition.
(I've seen this before)
'in set-to at hotel' is the wordplay.
'in' indicates the answer is hidden within the clue.
'OATH' is hidden within 'set to at hotel'.
'used' is the link.
(Other definitions for oath that I've seen before include "Courtroom promise" , "Swear word" , "bad language" , "Tedious task" , "A curse or solemn declaration" .)