Registered two types of drugs to make something with the same ingredients (6)
I believe the answer is:
rehash
'registered two' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for rehash that I've seen before include "That's nothing really new" , "Serve up old ideas" , "Recycled material" , "Use again, with few or no changes" , "Rework old material" .)