Certain to be in, since Germany is confident (7)
I believe the answer is:
assured
'confident' is the definition.
('assured' can be similar in meaning to 'confident')
'certain to be in since germany' is the wordplay.
'certain' becomes 'sure' ('sure' can be a synonym of 'certain').
'to be in' is an insertion indicator.
'since' becomes 'as' (I've seen this in other clues).
'germany' becomes 'd' (international vehicle registration code).
'as'+'d'='asd'
'sure' placed into 'asd' is 'ASSURED'.
'is' acts as a link.
(Other definitions for assured that I've seen before include "without doubt" , "Gave confidence to" , "Confident - certain" , "Secured" , "Promised, guaranteed" .)