Take the Sun King’s military vehicle (4)
I believe the answer is:
tank
'military vehicle' is the definition.
(armoured vehicle)
'take the sun king's' is the wordplay.
'take the sun' becomes 'tan' (I can't explain this - if you can you should give a lot more credence to this answer).
'king' becomes 'K' (abbreviation for king in chess).
'tan'+'k'='TANK'
Can you help me to learn more?
(Other definitions for tank that I've seen before include "Armoured vehicle; large container" , "Container for fish (or soldiers?)" , "Car fuel container" , "Large storage chamber" , "Army vehicle - reservoir" .)