Without opening, study container (3)
I believe the answer is:
can
'container' is the definition.
(can is a kind of container)
'without opening study' is the wordplay.
'without opening' means to remove the first letter.
'study' becomes 'scan' (I've seen this before).
'scan' with its first letter taken off is 'CAN'.
(Other definitions for can that I've seen before include "Tin; be able to" , "SECOND PART OF 10" , "toilet" , "John" , "May" .)