Article uncovered hate facing mostly left-wing arts arena (7)
I believe the answer is:
theatre
'arts arena' is the definition.
(arena or venue for an arts performance)
'article uncovered hate facing mostly left-wing' is the wordplay.
'article' becomes 'the' (the definite article in English).
'uncovered' means to look at the middle letters.
'facing' means one lot of letters go next to another.
'mostly' means to remove the last letter.
'left-wing' becomes 'red' (red can informally mean communist).
The middle of 'hate' is 'at'.
'red' with its last letter taken off is 're'.
'the'+'at'+'re'='THEATRE'
(Other definitions for theatre that I've seen before include "Where audiences may be present" , "US cinema" , "Scene of plays" , "Space for drama" , "World of drama" .)