Group of soldiers in club initially train a brave individual (9)
I believe the answer is:
battalion
'group of soldiers' is the definition.
'in club initially train a brave individual' is the wordplay.
'in' means one lot of letters goes inside another.
'club' becomes 'bat' (as in sporting equipment).
'initially' indicates taking the first letters.
'a brave' becomes 'alon' (I can't justify this - if you can you should believe this answer much more).
'individual' becomes 'i' (Roman numeral for one).
The first letter of 'train' is 't'.
'bat'+'t'+'alon'='battalon'
'battalon' going around 'i' is 'BATTALION'.
Can you help me to learn more?
(Other definitions for battalion that I've seen before include "army group" , "Army formation" , "Military unit" , "Army unit" , "many troops" .)