Capital required by old lover (5)
I believe the answer is:
romeo
'lover' is the definition.
(I've seen this before)
'capital required by old' is the wordplay.
'capital' becomes 'rome' (capital of Italy).
'required by' says to put letters next to each other.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'rome'+'o'='ROMEO'
(Other definitions for romeo that I've seen before include "Shakespearean lover" , "He's a letter read out" , "Comms code for R" , "Code word for the letter R" , "Juliet's immortal lover" .)