Its flow of water is right in volume (5)
I believe the answer is:
brook
'its flow' is the definition.
I can't judge whether this defines the answer.
'water is right in volume' is the wordplay.
'is right' indicates one should take the final letters (the letter on the right of the word).
'in' means one lot of letters goes inside another.
'volume' becomes 'book' (synonyms).
The last letter of 'water' is 'r'.
'r' inserted within 'book' is 'BROOK'.
'of' is the link.
Can you help me to learn more?
(Other definitions for brook that I've seen before include "Stand for" , "stomach" , "running water" , "Small fresh-water stream" , "Stream; put up with" .)