Talk tediously about old hunting weapon (7)
I believe the answer is:
harpoon
'hunting weapon' is the definition.
'talk tediously about old' is the wordplay.
'talk tediously' becomes 'harpon' (to harp on can mean to talk tediously).
'about' indicates putting letters inside.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'harpon' placed around 'o' is 'HARPOON'.
(Other definitions for harpoon that I've seen before include "Weapon for whales" , "Anti-whale weapon" , "Whaler's missile" , "Spear with a line attached for fishing" , "Whale-catching missile" .)