Foreign Office back on track? Absolutely (2,6)
I believe the answer is:
of course
'absolutely' is the definition.
(of course)
'foreign office back on track?' is the wordplay.
'foreign office' becomes 'FO' (abbreviation).
'back' says the letters should be written backwards.
'on' is a charade indicator (letters next to each other).
'track?' becomes 'course' ('course' can be a synonym of 'track').
'fo' backwards is 'of'.
'of'+'course'='OF COURSE'
(Other definitions for of course that I've seen before include "Naturally, as one would expect" , "need I say" , "Naturally, goes without saying" , "Definitely" , "without question" .)