Important meeting with German on the whole (6)
I believe the answer is:
summit
'important meeting' is the definition.
(I've seen this before)
'with german on the whole' is the wordplay.
'with german' becomes 'mit'.
'on' says to put letters next to each other.
'the whole' becomes 'sum' (sum is a kind of whole).
'mit' after 'sum' is 'SUMMIT'.
(Other definitions for summit that I've seen before include "High point" , "Top of a mountain, or meeting between heads of government" , "Topmost point" , "Talks" , "Pinnacle or crest" .)