Mr Scrooge welcomes ghost at the end (6)
I believe the answer is:
mister
'mr' is the definition.
(Mr is short for Mister)
'scrooge welcomes ghost at the end' is the wordplay.
'scrooge' becomes 'miser' (Dickens' Ebenezer Scrooge is a miser).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'at the end' suggests the final letters.
The final letter of 'ghost' is 't'.
'miser' enclosing 't' is 'MISTER'.
(Other definitions for mister that I've seen before include "Male form of address" , "Form of address to a man, used without his name" , "Bloke" , "Mr" , "Merits of form of address to man" .)