Struggle with weariness and shell shock (6,7)
I believe the answer is:
battle fatigue
'shell shock' is the definition.
(synonyms)
'struggle with weariness' is the wordplay.
'struggle' becomes 'battle' (a struggle or ordeal might be called a battle).
'with' says to put letters next to each other.
'weariness' becomes 'fatigue' (synonyms).
'battle'+'fatigue'='BATTLE FATIGUE'
'and' acts as a link.
(Other definitions for battle fatigue that I've seen before include "Stress from war" , "Shell shock" , "consequence of war" , "Mental disorder caused by stress in warfare" .)