Revolutionary American flag and tree (5)
I believe the answer is:
balsa
'tree' is the definition.
(balsa is a kind of tree)
'revolutionary american flag' is the wordplay.
'revolutionary' says the letters should be written backwards.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'flag' becomes 'slab' (flag can mean a stone slab).
'a'+'slab'='aslab'
'aslab' written backwards gives 'BALSA'.
'and' acts as a link.
(Other definitions for balsa that I've seen before include "Wood used in model making" , "Tropical American tree" , "Central American forest tree used to make floats, rafts, models etc" , "Very lightweight wood from tropical tree" , "Strong lightweight wood" .)