Letter puzzle (7)
I believe the answer is:
anagram
'letter puzzle' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for anagram that I've seen before include "Jumbling of letters" , "Word with rearrangeable letters" , "1d for instance" , "Word that rearranges another's letters" , "Word created from other word" .)