Hit, and unable to move across river (6)
I believe the answer is:
struck
'hit' is the definition.
(I've seen this before)
'unable to move across river' is the wordplay.
'unable to move' becomes 'stuck' (I've seen this before).
'across' is an insertion indicator.
'river' becomes 'r'.
'stuck' placed around 'r' is 'STRUCK'.
'and' is the link.
(Other definitions for struck that I've seen before include "set out" , "Given blows - affected instantaneously" , "Took industrial action" , "Delivered a sharp blow" , "Hit, knocked with blow" .)