A container slightly open (4)

I believe the answer is:

ajar

'slightly open' is the definition.
(as in a door left ajar)

'a container' is the wordplay.
'container' becomes 'jar' (jar is a kind of container).
'a'+'jar'='AJAR'

(Other definitions for ajar that I've seen before include "Not quite closed" , "Barely open" , "Unlatched" , "Mourn" , "Half-open" .)

I've seen this clue in The Guardian, The Times and The Sun.

Want a hint initially instead of a full solution? Install my app