Different date I require shortly — one being held (8)
I believe the answer is:
detainee
'one being held' is the definition.
(someone being detained)
'different date i require shortly' is the wordplay.
'different' indicates anagramming the letters.
'require shortly' becomes 'nee' (I can't explain this - if you can you should believe this answer much more).
'date' is an anagram of 'deta'.
'deta'+'i'+'nee'='DETAINEE'
(Other definitions for detainee that I've seen before include "Person kept in custody" , "Prisoner" , "confined person" , "One held in custody" , "One penned" .)