Train robbery (5-2)
I believe the answer is:
break in
This clue is a double definition.
'train' is the first definition.
(thesaurus)
'robbery' is the second definition.
(I've seen this in another clue)
(Other definitions for break in that I've seen before include "Criminal entry" , "Domesticate" , "Interrupt - burglary" , "Forced entry" , "Illegally enter" .)