Crossword Genius

Hardly a fast grower (7)

Ross

I believe the answer is:

creeper

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

'hardly a' is the wordplay.
'hardly' becomes 'cree' (I can't explain this - if you can you should believe this answer much more).
'a' becomes 'per' (eg 'one a day' means 'one per day').
'cree'+'per'='CREEPER'

'fast' acts as a link.

Can you help me to learn more?

(Other definitions for creeper that I've seen before include "Say, Virginia" , "Ivy or Virginia, for example" , "Variety of plant" , "Reptile" , "low-lying plant" .)

I've seen this clue in the Evening Standard.
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