22 down
Capital
both
sides
lost
in
trade
union’s
protest
(4)
Capital both sides lost in trade union’s protest (4)
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The definition is at the beginning of the clue.
How the clue works
Look at the bit after the apostrophe: a trade union's protest is a GO-SLOW, and "both sides lost" means you chop off the first and last letters (the G and the W), which leaves OSLO. The definition is just Capital, since Oslo is one.