A virile gent turns, enthralling 50 grown-ups (6)
I believe the answer is:
adults
'grown-ups' is the definition.
(a grown-up is an adult)
'a virile gent turns enthralling 50' is the wordplay.
'virile gent' becomes 'stud' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'turns' is a reversal indicator.
'enthralling' indicates putting letters inside.
'50' becomes 'l' (Roman numeral).
'stud' reversed gives 'duts'.
'duts' placed around 'l' is 'dults'.
'a'+'dults'='ADULTS'
Can you help me to learn more?
(Other definitions for adults that I've seen before include "Grown-up people" , "Fully-developed animals" , "Fully developed animals" , "Grown-upss" , "Fully developed and mature" .)