A number of Germans produced fiction (4)
I believe the answer is:
lied
'produced fiction' is the definition.
(I've seen this in another clue)
'a number of germans' is the wordplay.
'a number' becomes 'L' (fifty in Roman numerals).
'of germans' becomes 'ied' (I can't justify this - if you can you should give a lot more credence to this answer).
'l'+'ied'='LIED'
Can you help me to learn more?
(Other definitions for lied that I've seen before include "Made up a story" , "gave a false impression" , "Spoke falsely" , "piece of music" , "Stated falsely" .)