Altering course, sniper produces echo (12)
I believe the answer is:
repercussion
'echo' is the definition.
(thesaurus)
'altering course sniper' is the wordplay.
'altering' indicates anagramming the letters.
'course'+'sniper'='coursesniper'
'coursesniper' with letters rearranged gives 'REPERCUSSION'.
'produces' acts as a link.
(Other definitions for repercussion that I've seen before include "Backlash" , "Impact" , "Recoil; reverberation" , "Unintended consequence" , "Indirect consequence of some action" .)