Cave reached when going over river (6)
I believe the answer is:
grotto
'cave' is the definition.
(I know that grotto is a type of cave)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for grotto that I've seen before include "(Imitation) cave" , "A picturesque cave as in Lourdes (6)" , "Cavern" , "Fancy cave" , "Artificially or naturally ornamented cave" .)