American guy crosses river and leaves (5)
I believe the answer is:
chard
'leaves' is the definition.
(I know that Chard is a type of leaf vegetable)
'american guy crosses river' is the wordplay.
'american guy' becomes 'chad' (I can't justify this - if you can you should believe this answer much more).
'crosses' indicates putting letters inside.
'river' becomes 'r' (abbreviation).
'chad' going around 'r' is 'CHARD'.
'and' is the link.
Can you help me to learn more?
(Other definitions for chard that I've seen before include "Variety of beet with edible white leaf stalks" , "vegetable crop" , "Green vegetable" , "Leaf stalks from a kind of beet" , "Kind of (Swiss?) beet with edible leaves" .)