Hundred small river fish in the basket (5)
I believe the answer is:
creel
'basket' is the definition.
(basket for holding fish)
'hundred small river fish' is the wordplay.
'hundred' becomes 'c' (Roman numeral).
'small river' becomes 'r' (abbreviation for river; 'small' asks for an abbreviation).
'fish' becomes 'eel' (eel is a type of fish).
'c'+'r'+'eel'='CREEL'
'in the' acts as a link.
(Other definitions for creel that I've seen before include "Wickerwork basket" , "Fish-basket" , "Large fishing basket" , "Fisherman's basket" , "Basket (for a mackerel once caught?)" .)