American with second class property (5)
I believe the answer is:
asset
'property' is the definition.
(asset can mean an item of property)
'american with second class' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'with' means one lot of letters go next to another.
'second' becomes 's' (common abbreviation).
'class' becomes 'set' (I've seen this in other clues).
'a'+'s'+'set'='ASSET'
(Other definitions for asset that I've seen before include "good point" , "Useful item" , "A possession of some value" , "Advantage, strength" , "Help" .)