Transfer back (6)
I believe the answer is:
second
I believe this clue is a double definition.
'transfer' is the first definition.
(thesaurus)
'back' is the second definition.
('second' can be a synonym of 'back')
(Other definitions for second that I've seen before include "Short space of time" , "Support - runner-up" , "A boxer's corner assistant - not the first" , "Attendant in a duel or boxing match" , "Extra" .)