Unfortunate orphan pierced by old spear (7)
I believe the answer is:
harpoon
'spear' is the definition.
(I know that harpoon is a type of spear)
'unfortunate orphan pierced by old' is the wordplay.
'unfortunate' indicates anagramming the letters.
'pierced by' indicates putting letters inside (inserted letters pierce the word).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'orphan' anagrammed gives 'harpon'.
'harpon' going around 'o' is 'HARPOON'.
(Other definitions for harpoon that I've seen before include "Whaling weapon" , "Whale-catching missile" , "Whale spear" , "Weapon for whales" , "Whaler's weapon" .)