Full-grown graduate has true style (6)
I believe the answer is:
mature
'full-grown' is the definition.
(similar in meaning)
'graduate has true style' is the wordplay.
'graduate' becomes 'MA' (abbreviation for Master of Arts).
'has' says to put letters next to each other.
'style' indicates anagramming the letters (style can mean to shape or design).
'true' with letters rearranged gives 'ture'.
'ma'+'ture'='MATURE'
(Other definitions for mature that I've seen before include "Grown-up" , "Ripen or grow up" , "Old film star" , "Fully grown and adult" , "sensible" .)