Larger bachelor, German, holding US soldier up (6)
I believe the answer is:
bigger
'larger' is the definition.
('big' can be a synonym of 'large')
'bachelor german holding us soldier up' is the wordplay.
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'german' becomes 'ger' (abbreviation).
'holding' means one lot of letters goes inside another.
'us soldier' becomes 'gi' (informal term for a US soldier).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'gi' reversed gives 'ig'.
'b'+'ger'='bger'
'bger' placed around 'ig' is 'BIGGER'.
(Other definitions for bigger that I've seen before include "louder" , "Larger" , "Comparatively huge" , "Greater in size" .)