Legend of how silly rook fell (8)
I believe the answer is:
folklore
'legend of how silly rook fell' is the definition.
'folklore' can be an answer for 'legend' (thesaurus). I'm not certain of the 'of how silly rook fell' bit.
'silly rook fell' is the wordplay.
'silly' is an anagram indicator.
'rook'+'fell'='rookfell'
'rookfell' with letters rearranged gives 'FOLKLORE'.
Can you help me to learn more?
(Other definitions for folklore that I've seen before include "Traditional knowledge of a culture" , "Stories and legends" , "Ancient customs and beliefs" , "Traditional beliefs and tales of community" , "Stories, traditions, etc., of a group of people" .)