Tales about rock (5)
I believe the answer is:
slate
'rock' is the definition.
(slate is a type of stone)
'tales about' is the wordplay.
'about' indicates anagramming the letters.
'tales' is an anagram of 'SLATE'.
(Other definitions for slate that I've seen before include "Roofing plate" , "A roof-tile; criticise heavily" , "Criticise - outdated school equipment" , "Scold; hard rock" , "Bluish-grey colour" .)