What does the cryptic crossword clue "Boy everything’s too full-on at the end! (3)" mean?

The definition is "Boy". The wordplay uses acrostic. last letters of "everything's too full-on" = SON; definition: "Boy" The answer is SON.

Boy everything’s too full-on at the end! (3)

Independent Cryptic #11734 | 28 Across | 2024-05-20 flower