A chap of 50 nowadays? (3)
I believe the answer is:
lad
'a chap' is the definition.
('lad' can be a synonym of 'chap')
'50 nowadays?' is the wordplay.
'50' becomes 'l' ('L' can be a synonym of '50').
'nowadays?' becomes 'ad'.
'l'+'ad'='LAD'
'of' is the link.
(Other definitions for lad that I've seen before include "Shaver" , "Stable employee" , "Scottish lover" , "A young chap into ballads" , "Son" .)