Water may flow along this very narrow street (6)
I believe the answer is:
valley
'water may flow along this' is the definition.
The definition suggests a singular noun which matches the answer.
'very narrow street' is the wordplay.
'very' becomes 'v' (common abbreviation).
'narrow street' becomes 'alley' (I've seen this before).
'v'+'alley'='VALLEY'
Can you help me to learn more?
(Other definitions for valley that I've seen before include "Flat area of land flanked by hills" , "one running between hills" , "in victory with large marble" , "Dale, dene or glen" , "one depressed" .)