Hooray! Terrible eye-popping pong is gone (6)
I believe the answer is:
yippee
'hooray' is the definition.
(I've seen this before)
'terrible eye-popping pong is gone' is the wordplay.
'terrible' is an anagram indicator.
'is gone' suggests deleting specific letters.
'eye'+'popping'='eyepopping'
'eyepopping' with 'pong' taken out is 'eyeppi'.
'eyeppi' with letters rearranged gives 'YIPPEE'.
(Other definitions for yippee that I've seen before include "Hurray" , "That's wonderful!" , "Excellent!" , "Hooray!" , "Cry of wild delight" .)