Checked before a heist (5)
I believe the answer is:
cased
'checked before a heist' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cased that I've seen before include "Covered, protected; checked over (by robber)" , "examined with intention to rob" , "Carefully inspected (for crime)" , "put in a box" , "Reconnoitred (sl.)" .)