Stream for hire, including river (7)
I believe the answer is:
torrent
'stream' is the definition.
(I know that torrent is a type of stream)
'for hire including river' is the wordplay.
'for' becomes 'to' (eg both can mean 'in the opinion of').
'hire' becomes 'rent' (synonyms).
'including' indicates putting letters inside.
'river' becomes 'r' (abbreviation).
'rent' going around 'r' is 'rrent'.
'to'+'rrent'='TORRENT'
(Other definitions for torrent that I've seen before include "Overwhelming deluge" , "Overwhelming flood" , "A rushing stream of water" , "Heavy flow of water" , "Inundation" .)