A Shakespearean character needs it back by Monday (5)
I believe the answer is:
timon
'a shakespearean character' is the definition.
(Timon of Athens)
'it back by monday' is the wordplay.
'back' shows that the letters should be reversed in order.
'by' says to put letters next to each other.
'monday' becomes 'Mon' (short for Monday).
'it' in reverse letter order is 'ti'.
'ti'+'mon'='TIMON'
'needs' acts as a link.
(Other definitions for timon that I've seen before include "part of Shakespeare" , "legendary misanthrope" , "-- of Athens (play)" , "Greek misanthrope in play" , "Shakespearean Athenian" .)