Worries about muck up by German magazines (10)
I believe the answer is:
cartridges
'magazines' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Maybe there's an association between them I don't understand?
'worries about muck up by german' is the wordplay.
'worries' becomes 'cares' (I've seen this before).
'about' is an insertion indicator.
'muck' becomes 'dirt' (I've seen this before).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'by german' becomes 'g' (abbreviation. I am not sure about the 'by' bit.**).
'dirt' back-to-front is 'trid'.
'trid'+'g'='tridg'
'cares' going around 'tridg' is 'CARTRIDGES'.
Can you help me to learn more?
(Another definition for cartridges that I've seen is " containers".)