Crossword Genius

Trying to excise mass: no significant growth (7)

Ross

I believe the answer is:

sapling

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

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for sapling that I've seen before include "Little tree" , "Lapsing into a young tree" , "Poetic youth" , "Baby tree" , "Young slender tree" .)

I've seen this clue in The Sun.
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