Soldier in appropriate American gear (9)
I believe the answer is:
apparatus
'gear' is the definition.
(thesaurus)
'soldier in appropriate american' is the wordplay.
'soldier' becomes 'para' (para is a kind of soldier**).
'in' means one lot of letters goes inside another.
'appropriate' becomes 'apt' ('apt' can be a synonym of 'appropriate').
'american' becomes 'us'.
'para' going within 'apt' is 'apparat'.
'apparat'+'us'='APPARATUS'
(Other definitions for apparatus that I've seen before include "Machinery" , "political organisation" , "Collection of equipment designed for a particular purpose" , "Piece of equipment" , "Set of equipment serving a specific purpose" .)