Five characters, wolves in disguise (6)
I believe the answer is:
vowels
'five characters' is the definition.
(the vowels A, E, I, O and U)
'wolves in disguise' is the wordplay.
'in disguise' indicates an anagram.
'wolves' with letters rearranged gives 'VOWELS'.
(Other definitions for vowels that I've seen before include "aeiou" , "Speech sounds made with the vocal tract open" , "A e i o u" , "'Five letters, not consonants (6)'" , "Five speech sounds" .)