Struggle with editor's extremes in the Spectator (6)
I believe the answer is:
viewer
'spectator' is the definition.
(synonyms)
'struggle with editor's extremes' is the wordplay.
'struggle' becomes 'vie' (I've seen this before).
'with' becomes 'w' (abbreviation).
'extremes' suggests removing the centre.
'editor' with its centre taken out is 'er'.
'vie'+'w'+'er'='VIEWER'
'in the' acts as a link.
(Other definitions for viewer that I've seen before include "One who watches, say, TV" , "Onlooker" , "Observer" , "One seeing" , "Review for TV watcher" .)