A case that is hard to project in attack (5)
I believe the answer is:
shell
This clue might be a double definition.
'a case that is hard to project' is the first definition.
'shell' can be an answer for 'a case' (synonyms). I'm unsure of the remainder of the definition.
'attack' is the second definition.
(I know that shell is a more specific form of the action bomb)
'in' is the link.
Can you help me to learn more?
(Other definitions for shell that I've seen before include "Mollusc's casing" , "pepper?" , "magazine article" , "Empty case" , "Explosive projectile" .)