Crossword Genius

Nothing to write? That's clear (4)

Ross

I believe the answer is:

open

'clear' is the definition.
('open' can be a synonym of 'clear')

'nothing to write?' is the wordplay.
'nothing' becomes 'o' (looks like zero - 0).
'to write?' becomes 'pen' ('pen' can be a synonym of 'write').
'o'+'pen'='OPEN'

'that's' is the link.

(Other definitions for open that I've seen before include "golf contest" , "Willing" , "Liberal" , "Candid and undisguised" , "Not shut or secret" .)

I've seen this clue in The Telegraph.
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