Equine sheep beyond a mix-up of characters! (7)
I believe the answer is:
anagram
'mix-up of characters' is the definition.
'anagram' can be an answer for 'mix-up' (I've seen this before). I'm not sure about the 'of characters' bit.
'equine sheep beyond a' is the wordplay.
'equine' becomes 'nag' (nag is a kind of equine).
'sheep' becomes 'ram' (male sheep).
'beyond' is a charade indicator (letters next to each other).
'nag'+'ram'='nagram'
'nagram' put after 'a' is 'ANAGRAM'.
Can you help me to learn more?
(Other definitions for anagram that I've seen before include "Type of word puzzle" , "1d for instance" , "Shuffling of letters" , "Cruciverbal jumble" , "Word arranging the letters of another" .)