Something to eat when the river is frozen? (4)
I believe the answer is:
rice
'something to eat' is the definition.
(rice is a kind of food)
'the river is frozen?' is the wordplay.
'the river' becomes 'r'.
'is frozen?' becomes 'ice' (I've seen this in other clues**).
'r'+'ice'='RICE'
'when' acts as a link.
(Other definitions for rice that I've seen before include "Cereal grown in paddy fields" , "Grain from the paddy field" , "... his librettist - cereal" , "Type of grain" , "Curry side dish" .)