... about a thin wound in the novel (9)
I believe the answer is:
whodunnit
'novel' is the definition.
'about a thin wound' is the wordplay.
'about' indicates an anagram.
'thin'+'wound'='thinwound'
'thinwound' anagrammed gives 'WHODUNNIT'.
'in the' acts as a link.
(Other definitions for whodunnit that I've seen before include "yarn unravelled finally?" , "Detective story" , "crime novel" , "book" , "literary mystery" .)