* Key Trump adviser resigns
(Recasts, adds quote and detail, updates prices at close):
LONDON (Reuters) - European shares clawed back losses on Wednesday as deal-making speculation reinvigorated trading following a muted start to the session. The pan-European STOXX 600 index ended with a gain of 0.4 percent, climbing steadily through the day and shaking off worries over the resignation of Donald Trump’s economic adviser Gary Cohn, seen as a bulwark against protectionist forces within the U.S. government. Shares on Wall Street fell.