Rear admiral dismisses alarm produced by pirate (6)
I believe the answer is:
raider
'pirate' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for raider that I've seen before include "Armed insurgent" , "person who's involved in sacking?" , "One attacks" , "One making incursion" , "Pillager, plunderer" .)