BUZZ-Clarkson: worst day in 8.5 mths on stake sale
** Shipping services provider Clarkson -4.4%, falls off record high & top of FTSE 250 losers' list
** Former investors of RS Platou ASA, a co bought by Clarkson (LSE: CKN.L - news) last Feb, sell about 1.23 mln shares, or about 4.1 pct stake in co
** Sale priced at 2,750 p/shr vs Tues close of 2,951 p/shr
** Stock reached record in the wake of higher FY results earlier this yr (+36% YTD vs +5% midcap index)
** On Wed after stake sale announcement, stock heads towards worst day since July; co not to share in any proceeds
** Easily most-actively traded stock among midcaps, with >19.5X 30-day avg vol through in 20 mins of trade