What does the cryptic crossword clue "'Grow up pal', she said, 'you are in' (6)" mean?

The definition is "Grow up". The wordplay uses a homophone (sounds like). Homophone [ she said ] of YOU ARE in MATE (“pal”) The answer is MATURE.

'Grow up pal', she said, 'you are in' (6)

Guardian Cryptic #28962 | 9 Across | 2023-01-09 flower