Lacking will to cross river the American way? (10)
I believe the answer is:
interstate
'american way?' is the definition.
(I've seen this before)
'lacking will to cross river' is the wordplay.
'lacking will' becomes 'intestate'.
'to cross' means one lot of letters goes inside another.
'river' becomes 'r' (abbreviation for river).
'intestate' placed around 'r' is 'INTERSTATE'.
'the' acts as a link.
(Other definitions for interstate that I've seen before include "between parts of US" , "road in US" , "American way" , "American motorway" , "highway" .)