Indirect anagram

In crossword lore, an indirect anagram is a type of wordplay involving an anagram of a word or phrase for which a synonym is given in place of the letters themselves.

Example
Consider the clue Unusually tough monster (5), adapted from an example given in Ximenes on the Art of the Crossword. Here, the compiler has invoked the indirect anagram: the solver is expected first to find the synonym "hardy" for "tough", and then to anagram it to give the answer "hydra", as opposed to being given the clue "Unusually hardy monster (5)", in which the letters to be anagrammed are provided literatim.

History
During the formative years of the modern cryptic clue, indirect anagrams were commonplace, with setters as high profile as Afrit and Ximenes routinely using them, even with rare and difficult words.