Weapon's steady holding attention (7)
I believe the answer is:
firearm
'weapon's' is the definition.
(firearm is a kind of weapon)
'steady holding attention' is the wordplay.
'steady' becomes 'firm' ('firm' can be a synonym of 'steady').
'holding' indicates putting letters inside.
'attention' becomes 'ear' (ear is a kind of attention).
'firm' enclosing 'ear' is 'FIREARM'.
(Other definitions for firearm that I've seen before include "Hand-held weapon" , "Colt possibly" , "One's fired" , "Pistol, rifle or gun" , "Rod" .)