10 across
Against
being
briefly
affirmative
in
written
opinion
(7)
Against being briefly affirmative in written opinion (7)
hints
0
checks
0
hints
The definition is at the beginning of the clue.
How the clue works
The definition is Against. briefly affirmative gives you POS — short for POSitive — and that gets slotted into op-ed, your written opinion piece, to give you OP + POS + ED.