Police arrest leading lad shooting darts (5)
I believe the answer is:
cupid
'lad shooting darts' is the definition.
(Roman god that shoots arrows)
'police arrest leading' is the wordplay.
'police' becomes 'CID' (abbreviation for Criminal Investigation Department).
'arrest' indicates putting letters inside.
'leading' becomes 'up' (up can mean leading in a game).
'cid' placed around 'up' is 'CUPID'.
(Other definitions for cupid that I've seen before include "godlike figure" , "Tiny archer as Roman god of love" , "Blind god" , "naked boy" , "heathen god" .)