Helps king to pre-empt attacks (5)
I believe the answer is:
raids
'attacks' is the definition.
(raiding is a kind of attacking)
'helps king to pre-empt' is the wordplay.
I cannot quite see how this works, but
'helps' could be 'aids' ('aid' can be a synonym of 'help') and 'aids' is located in the answer.
'king' could be 'r' (abbreviation of Latin rex) and 'r' is found within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for raids that I've seen before include "Searches by police without warning" , "Military attacks" , "Sudden attacks" , "Invasions" , "Military incursions, forays" .)