Troy's mistake creating panic (6)
I believe the answer is:
terror
'panic' is the definition.
(I know that panic can be written as terror)
'troy's mistake' is the wordplay.
'troy' becomes 't'.
'mistake' becomes 'error' (synonyms).
't'+'error'='TERROR'
'creating' acts as a link.
(Other definitions for terror that I've seen before include "Troublesome kid" , "Extreme or intense fear" , "Abject fear" , "Extreme fear of dread" , "Little brat" .)