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 really 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 in the answer.
This accounts for all the letters.
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" .)