Book open, fantastically intense (12)
I believe the answer is:
frankenstein
'book' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see an association between them that I can't see?
'open fantastically intense' is the wordplay.
'open' becomes 'frank' (synonyms).
'fantastically' indicates an anagram (a fantastical ordering of the letters).
'intense' with letters rearranged gives 'enstein'.
'frank'+'enstein'='FRANKENSTEIN'
Can you help me to learn more?
(Other definitions for frankenstein that I've seen before include "that could ruin manufacturer" , "Monster inventor" , "Mary Shelley novel" , "Mary Shelley's monster" , "Monstrous and dangerous humanoid" .)