Try to tackle criminal? (4,1,2)
I believe the answer is:
have a go
I believe this is a double definition.
'try' is the first definition.
(to have a go is to make an attempt)
'tackle criminal?' is the second definition.
(I've seen this before)
'to' acts as a link.
(Other definitions for have a go that I've seen before include "Take a turn" , "Make an attempt" , "Words of encouragement" , "Tackle criminal" , "Intervening to stop a criminal (colloq,)" .)