Army branch beer, say, is US property (4,6)
I believe the answer is:
real estate
'us property' is the definition.
'real estate' can be an answer for 'property' (real estate is a kind of property). I'm unsure of the 'us' bit.
'army branch beer say' is the wordplay.
'army' becomes 'RE' (Royal Engineers regiment).
'branch beer' becomes 'ale' (I can't explain this - if you can you should give a lot more credence to this answer).
'say' becomes 'state' (synonyms).
're'+'ale'+'state'='REAL ESTATE'
'is' is the link.
Can you help me to learn more?
(Other definitions for real estate that I've seen before include "land in New England" , "properties" , "Property, land (esp. US)" , "Land (mainly US)" , "Landed property" .)