Develop into adulthood (6)
I believe the answer is:
mature
(Other definitions for mature that I've seen before include "Grow older" , "Fully grown and developed (6)" , "due to be paid" , "Fully grown and adult" , "Age" .)
I believe the answer is:
mature
(Other definitions for mature that I've seen before include "Grow older" , "Fully grown and developed (6)" , "due to be paid" , "Fully grown and adult" , "Age" .)