That woman will be a hard case! (5)
I believe the answer is:
shell
This could be a double definition.
'that woman will' is the first definition.
(I've seen this in other clues)
'a hard case' is the second definition.
'shell' can be an answer for 'case' (shell is a kind of case). I'm unsure of the 'a hard' bit.
'be' is the link.
Can you help me to learn more?
(Other definitions for shell that I've seen before include "magazine article" , "Hard case; projectile" , "attack with bombs" , "Hard outer covering" , "Outside of an egg" .)