Control, gained through force by fraud on a mission (8)
I believe the answer is:
conquest
'control gained through force' is the definition.
I can't tell whether this definition defines the answer.
'fraud on a mission' is the wordplay.
'fraud' becomes 'con' (con is a kind of fraud).
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'a mission' becomes 'quest' (a quest is a mission or search).
'con'+'quest'='CONQUEST'
'by' is the link.
Can you help me to learn more?
(Other definitions for conquest that I've seen before include "Catch" , "occupied territory" , "Victory by force" , "leads to defeat" , "The subjugation and assumption of control by military force" .)