The maxim of many a German (5)
I believe the answer is:
motto
'the maxim' is the definition.
(thesaurus)
'many a german' is the wordplay.
'many' becomes 'm' (**).
'a german' becomes 'otto' (I've seen this before).
'm'+'otto'='MOTTO'
'of' acts as a link.
(Other definitions for motto that I've seen before include "Saw" , "cry" , "Short sentence expressing an ideal" , "Cracker slip" , "device" .)