Dye covering half of hair in helmet (3,3)
I believe the answer is:
tin hat
'helmet' is the definition.
(tin hat is a kind of helmet)
'dye covering half of hair' is the wordplay.
'dye' becomes 'tint' (tinting is a kind of dyeing).
'covering' means one lot of letters goes inside another.
'half of' suggests halving the letters.
'hair' with half the letters taken is 'ha'.
'tint' enclosing 'ha' is 'TIN HAT'.
'in' is the link.
(Other definitions for tin hat that I've seen before include "Soldier's helmet" , "Steel helmet (informal)" , "Protective helmet once worn by constuction and mine workers" , "Finish it off to put the protective headgear on it" , "Headgear, worn for protection" .)