Soldier receives second posh volume (6)
I believe the answer is:
amount
'volume' is the definition.
(thesaurus)
'soldier receives second posh' is the wordplay.
'soldier' becomes 'ant' (I've seen this before).
'receives' indicates putting letters inside.
'second' becomes 'mo' (both are short periods of time).
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-u).
'mo'+'u'='mou'
'ant' placed around 'mou' is 'AMOUNT'.
(Other definitions for amount that I've seen before include "value" , "Measure, quantity" , "Size" , "Supply" , "Quantity, sum" .)