Tom possibly injured Paul with tip of this weapon (8)
I believe the answer is:
catapult
'weapon' is the definition.
(I've seen this before)
'tom possibly injured paul with tip of this' is the wordplay.
'tom possibly' becomes 'cat' (a tom is a male cat).
'injured' indicates an anagram.
'with' means one lot of letters go next to another.
'tip of' says to take the initial letters.
The first letter of 'this' is 't'.
'paul' with letters rearranged gives 'apul'.
'cat'+'apul'+'t'='CATAPULT'
(Other definitions for catapult that I've seen before include "Stone-throwing device" , "Slingshot" , "fling" , "Hurl forcibly as from sling" , "Weapon projecting stones" .)