Now play around with some darts (5)
I believe the answer is:
today
'now' is the definition.
(I've seen this before)
'play around with some darts' is the wordplay.
'play' becomes 'toy' ('toy' can be a synonym of 'play').
'around' means one lot of letters goes inside another.
'with some darts' becomes 'da' (I can't explain this - if you can you should give a lot more credence to this answer).
'toy' going around 'da' is 'TODAY'.
(Other definitions for today that I've seen before include "Current period of 24 hours" , "Presently" , "12, 12" , "Nowadays" , "At the present time, in general" .)