Vessels in decay loaded with iron on banks of river (3,7)

'vessels' is the definition.
(car-ferry is a kind of vessel)

'decay loaded with iron on banks of river' is the wordplay.
'decay' becomes 'caries' (dental caries).
'loaded with' means one lot of letters goes inside another.
'iron on' becomes 'fe' (Fe is the chemical symbol for iron. I am not sure about the 'on' bit.).
'banks of' suggests removing the centre (the banks are the sides of the word).
'river' with its middle removed is 'rr'.
'fe'+'rr'='ferr'
'caries' going around 'ferr' is 'CAR-FERRIES'.

'in' is the link.