What does the cryptic crossword clue "Any of five letters read out is a confession (6)" mean?

The definition is "confession". The wordplay uses a homophone (sounds like). Sounds like “a vowel”, i.e. one of AEIOU The answer is AVOWAL.

Any of five letters read out is a confession (6)

Guardian Cryptic #29196 | 2 Down | 2023-10-09 flower