Weapon causing pilots to crash (6)
I believe the answer is:
pistol
'weapon' is the definition.
(pistol is a kind of weapon)
'pilots to crash' is the wordplay.
'to crash' is an anagram indicator.
'pilots' with letters rearranged gives 'PISTOL'.
'causing' acts as a link.
(Other definitions for pistol that I've seen before include "making an appearance in Shakespeare's King Henry V" , "Piece" , "Shakespearean character" , "Spoilt these guns" , "Small gun" .)