Nag about German group (4)
I believe the answer is:
gang
'group' is the definition.
(a gang is a group of people)
'nag about german' is the wordplay.
'about' shows that the letters should be reversed in order.
'german' becomes 'g' (abbreviation).
'nag' written backwards gives 'gan'.
'gan'+'g'='GANG'
(Other definitions for gang that I've seen before include "Informal body of friends" , "Posse" , "Crew, band" , "Organised group of labourers" , "set of tools" .)