Before robbery, looking over enclosure (6)
I believe the answer is:
casing
I believe this clue is a double definition.
'before robbery looking over' is the first definition.
(as in casing a joint before robbing it)
'enclosure' is the second definition.
(Other definitions for casing that I've seen before include "Outer protective covering" , "Recceing" , "Protective shell" , "Outer covering of something" , "Outside cover" .)