It grows dome-shaped (5)

I believe the answer is:

onion

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'it grows dome-shaped' is the definition.
The definition suggests a singular noun which matches the answer.

This is all the clue.

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(Other definitions for onion that I've seen before include "Tear-inducing edible bulb" , "associated with 26 [TRIPE] ?" , "Head (slang); vegetable" , "Plant with edible bulb" , "Shape of Russian dome" .)

I've seen this clue in the Evening Standard.

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