Crossword Genius

At home, its contents may well be growing (7)

Ross

I believe the answer is:

planter

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'at' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

I cannot understand how the remainder of the clue works.

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(Other definitions for planter that I've seen before include "Sowing machine" , "Settler or colonizer" , "Decorative pot" .)

I've seen this clue in the Evening Standard.
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