Current age of US lawman given in play (5)
I believe the answer is:
today
'current age' is the definition.
'us lawman given in play' is the wordplay.
'us lawman' becomes 'da' (district attorney).
'given in' is an insertion indicator.
'play' becomes 'toy' ('toy' can be a synonym of 'play').
'da' going into 'toy' is 'TODAY'.
'of' is the link.
(Other definitions for today that I've seen before include "At the present time, in general" , "Modern times" , "Nowadays" , "one of our papers, once" , "Presently" .)