Missing person dispatched during a competition (8)
I believe the answer is:
absentee
'missing person' is the definition.
(I've seen this before)
'dispatched during a competition' is the wordplay.
'dispatched' becomes 'sent' (I've seen this before).
'during' indicates putting letters inside.
'competition' becomes 'bee' (I've seen this before).
'a'+'bee'='abee'
'sent' put within 'abee' is 'ABSENTEE'.
(Other definitions for absentee that I've seen before include "Someone not present" , "Deserter - truant b" , "One is not present when required" , "One who should be but isn't present" , "One who stays away" .)