Open some beer (4)
I believe the answer is:
ajar
'open' is the definition.
(similar in meaning)
'some beer' is the wordplay.
'some' becomes 'a'.
'beer' becomes 'jar' (I've seen this before).
'a'+'jar'='AJAR'
(Other definitions for ajar that I've seen before include "Half-open" , "Unlatched" , "Mourn" , "Half open" , "Not quite shut" .)