A grate partly open (4)

I believe the answer is:

ajar

'partly open' is the definition.
(I've seen this before)

'a grate' is the wordplay.
'grate' becomes 'jar' (I've seen this before).
'a'+'jar'='AJAR'

(Other definitions for ajar that I've seen before include "not entirely open" , "letting in a little light?" , "(Door) to, not shut" , "near closing?" , "Half-closed" .)

I've seen this clue in The Telegraph.

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