Combatant's helmet that restricts batting (3,3)
I believe the answer is:
tin hat
'combatant's helmet' is the definition.
'that restricts batting' is the wordplay.
'restricts' is an insertion indicator.
'batting' becomes 'in'.
'that' going around 'in' is 'TIN HAT'.
(Other definitions for tin hat that I've seen before include "Soldier's helmet" , "Headgear, worn for protection" , "Protective helmet once worn by constuction and mine workers" , "Steel helmet (informal)" , "Finish it off to put the protective headgear on it" .)