Weapon for a ship, for example, first-class (7)
I believe the answer is:
assegai
'weapon' is the definition.
(assegai is a kind of weapon)
'a ship for example first-class' is the wordplay.
'ship' becomes 'ss'.
'for example' becomes 'e.g.' (synonyms).
'first class' becomes 'ai' (A1 - top quality).
'a'+'ss'+'eg'+'ai'='ASSEGAI'
'for' acts as a link.
(Other definitions for assegai that I've seen before include "Sea gas I convert to a Zulu spear" , "Spear of the Bantu-speaking people of Africa" , "Zulu fighting spear" , "African weapon" , "Wooden spear of southern Africa" .)