Book in deal that's broken (6)
I believe the answer is:
daniel
'book' is the definition.
(book of the Bible)
'in deal that's broken' is the wordplay.
'that's broken' indicates anagramming the letters.
'in'+'deal'='indeal'
'indeal' with letters rearranged gives 'DANIEL'.
(Other definitions for daniel that I've seen before include "-- Defoe; -- Barenboim" , "Craig, Day-Lewis or Radcliffe?" , "Old Testament character found in a den of lions" , "He interpreted Belshazzar's fate" , "Lions' den survivor" .)