Person turning up ruined teen date (8)
I believe the answer is:
attendee
'person turning up' is the definition.
I know nothing about this answer so I can't judge whether this works.
'ruined teen date' is the wordplay.
'ruined' is an anagram indicator.
'teen'+'date'='teendate'
'teendate' anagrammed gives 'ATTENDEE'.
Can you help me to learn more?
(Other definitions for attendee that I've seen before include "One shows up" , "Someone who is here" , "Person who is present at an event" , "Conference participant" , "One going to, eg, conference" .)