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