They enter by force to conquer (8)
I believe the answer is:
invaders
'they enter by force to conquer' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for invaders that I've seen before include "Intruding army" , "They enter by force in order to conquer" , "Attackers entering another country" , "Plunderers" , "Intruders, conquerers" .)