One ready to cross loch and land in river? (5)
I believe the answer is:
islet
'land in river?' is the definition.
(I've seen this before)
'one ready to cross loch' is the wordplay.
'one' becomes 'i' (Roman numeral).
'ready to' becomes 'set' (synonyms).
'cross' is an insertion indicator.
'loch' becomes 'l'.
'set' going around 'l' is 'slet'.
'i'+'slet'='ISLET'
'and' is the link.
(Other definitions for islet that I've seen before include "A small piece of territory" , "Cay, for example" , "Ait or eyot" , "Stile (anag)" , "small key?" .)