New mission to support military commander in victory (8)
I believe the answer is:
conquest
'victory' is the definition.
(I've seen this before)
'new mission to support military commander' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'mission' becomes 'quest' (I've seen this before).
'to support' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'military commander' becomes 'co' (I am not sure about the 'military' bit.).
'n'+'quest'='nquest'
'nquest' put after 'co' is 'CONQUEST'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for conquest that I've seen before include "Victory, triumph" , "Vanquishment" , "Taking of another's territory" , "leads to defeat" , "Victory over the enemy" .)