Crossword Genius

Laughably derisive about right flower border (9)

Ross

I believe the answer is:

riverside

I'm a little stuck... Click here to teach me more about this clue!

'laughably derisive about right' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'flower border' is the wordplay.
'flower' becomes 'river' (A river flows and is therefore a flower).
'border' becomes 'side' (I've seen this in other clues).
'river'+'side'='RIVERSIDE'

Can you help me to learn more?

(Other definitions for riverside that I've seen before include "Bank" , "Area along, say, the Thames" .)

I've seen this clue in The Telegraph.
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