Rearrangement of letters (7)
I believe the answer is:
anagram
'rearrangement of letters' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for anagram that I've seen before include "A ragman (anag)" , "Nag a ram (anag)" , "There's confusion among characters" , "Scramble of letters (to make trestle, perhaps)" , ""Diagnose" is one of "San Diego"" .)