Assemble for review, dropping book with which one’s spotted (7)
I believe the answer is:
measles
'book with which one's spotted' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for measles that I've seen before include "Morbilli is technical term for this illness" , "I appear as 8 [RASH]" , "Children's disease with red spots" , "Rash-causing disease" , "Rubeola" .)