Hounds struggling in river (6)
I believe the answer is:
'river' is the definition.
(I know that Hudson is a river)
'hounds struggling' is the wordplay.
'struggling' indicates an anagram.
'hounds' anagrammed gives 'HUDSON'.
'in' acts as a link.
(Other definitions for hudson that I've seen before include "New York river; Upstairs/ Downstairs butler" , "American banker" , "Rock -, - bay" , "River in New York city" , "Major inland sea of NE Canada - . . . . . . Bay" .)