Combined home working with back in office (2,3)
I believe the answer is:
in one
'combined' is the definition.
(as in 'all in one')
'home working with back in office' is the wordplay.
'home' becomes 'in' ('he's home' can mean 'he's in').
'working' becomes 'on' (e.g. a machine is working or on).
'with' is a charade indicator (letters next to each other).
'back in' says to take the final letters (the 'back' of the word).
The final letter of 'office' is 'e'.
'in'+'on'+'e'='IN ONE'
(Other definitions for in one that I've seen before include "Combined" , "As a single unit" , "united" , "A hole . . . . . is a singular golf score" .)