Greek warrior with a javelin's tip and short weapon (4)
I believe the answer is:
ajax
'greek warrior' is the definition.
(I've seen this in another clue)
'with a javelin's tip and short weapon' is the wordplay.
'with' is an insertion indicator.
'tip' says to take the initial letters (one tip of the word).
'short' says to take the initial letters.
'weapon' becomes 'ax' (an axe might be used as a weapon).
The initial letter of 'javelins' is 'j'.
The first letter of 'and' is 'a'.
'a'+'ax'='aax'
'j' put within 'aax' is 'AJAX'.
(Other definitions for ajax that I've seen before include "Hero of Greek mythology" , "Strong Gr. hero (Iliad)" , "Ancient Greek hero" , "Greek warrior (Iliad)" , "Old war hero" .)