Ugly sight I witnessed in the auditorium (7)
I believe the answer is:
eyesore
'ugly sight' is the definition.
(I've seen this before)
'i witnessed in the auditorium' is the wordplay.
I cannot quite see how this works, but
'i' could be 'eye' (I've seen this in other clues) and 'eye' is present in the answer.
The remaining letters 'sore' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for eyesore that I've seen before include "pigsty" , "Ugly structure" , "It's offensively ugly" , "Something ugly to look at" , "Blight" .)