German lopes about, in truth (6)
I believe the answer is:
gospel
'truth' is the definition.
(e.g. you can take is as gospel)
'german lopes about in' is the wordplay.
'german' becomes 'g' (abbreviation).
'about' indicates anagramming the letters.
'in' means one lot of letters goes inside another.
'lopes' with letters rearranged gives 'ospel'.
'g' inserted into 'ospel' is 'GOSPEL'.
(Other definitions for gospel that I've seen before include "One of the first four Books of the New Testament" , "sacred text" , "Truth (religious)" , "Black evangelical singing" , "Unquestionable truth - church doctrine" .)