Crossword Genius

Not really a shutter, nevertheless nearer the mark (6)

Ross

I believe the answer is:

closer

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'not really a shutter nevertheless' is the definition.
I can't judge whether this definition defines the answer.

'nearer the mark' is the wordplay.
'nearer' becomes 'close' (similar in meaning).
'the mark' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'close'+'r'='CLOSER'

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(Other definitions for closer that I've seen before include "more reticent" , "Comparatively near" , "denser" , "One winds up" , "Cresol (anag.)" .)

I've seen this clue in the Evening Standard.
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