Ring road constructed over East River (3,6)
I believe the answer is:
rio grande
'river' is the definition.
(Rio Grande is an example)
'ring road constructed over east' is the wordplay.
'constructed' indicates anagramming the letters.
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'east' becomes 'e' (abbreviation).
'ring'+'road'='ringroad'
'ringroad' anagrammed gives 'riogrand'.
'riogrand'+'e'='RIO GRANDE'
(Other definitions for rio grande that I've seen before include "American flower" , "banker" , "River boundary between the US and Mexico" , "River flowing between USA and Mexico" , "US/Mexican border river" .)