Tolerate a stream (5)
I believe the answer is:
brook
This clue is a double definition.
'tolerate' is the first definition.
('brook' can be a synonym of 'tolerate')
'a stream' is the second definition.
(brook is a kind of stream)
(Other definitions for brook that I've seen before include "Stand for" , "Stream; put up with" , "running water" , "stomach" , "Small fresh-water stream" .)