Grown-up (5)
'grown-up' is the definition.
(informal term for an adult)
This is all the clue.
(Other definitions for adult that I've seen before include "No child" , "Mature - grown-up" , "one no longer in minority" , "Person of mature age" , "X-rated?" .)
'grown-up' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mature that I've seen before include "Grow older" , "Fully developed physically" , "Ripe or fully grown" , "sensible" , "Age" .)