Image of German holding most of 6 down (6)
I believe the answer is:
vision
'image' is the definition.
(thesaurus)
'of german holding most of 6 down' is the wordplay.
'of german' becomes 'von' (common German surname element meaning 'of').
'holding' indicates putting letters inside.
'most of' means to remove the first letter.
'6' becomes 'vi' ('VI' can be a synonym of '6').
'down' becomes 'si' (I can't justify this - if you can you should give a lot more credence to this answer).
'vi' with its first letter removed is 'i'.
'i'+'si'='isi'
'von' going around 'isi' is 'VISION'.
(Other definitions for vision that I've seen before include "With it one perceives" , "Imagination" , "Perception by eye" , "See 24" , "Ability to see (6)." .)