Possible place for setter’s cryptic legend on back of book (3-6)
I believe the answer is:
dog-kennel
'possible place for setter's' is the definition.
(setter is a type of dog)
'cryptic legend on back of book' is the wordplay.
'cryptic' indicates anagramming the letters (I've seen this in other clues).
'back of' says to take the final letters.
The last letter of 'book' is 'k'.
'legend'+'on'+'k'='legendonk'
'legendonk' with letters rearranged gives 'DOG-KENNEL'.
(Other definitions for dog-kennel that I've seen before include "Labrador's home?" , "House for pet" .)