Shouts of triumph? I made a mistake (6)
I believe the answer is:
whoops
I believe this clue is a double definition.
'shouts of triumph?' is the first definition.
(whoop can mean a cheer)
'i made a mistake' is the second definition.
('whoops' can be an acknowledgement of an error)
(Other definitions for whoops that I've seen before include "Oh dear! That was a mistake!" , "Worrying cry" , "Something said after minor accident or mistake" , "Yikes, I've dropped something!" , "Exclamation after making a mistake" .)