This is a bid showing values in the suit bid as well as support for partner. It usually occurs after the bidder has already passed or taken some other action that precludes a purely natural interpretation of the bid.
Having turned down the easy chance to bid some number of clubs as dealer, West can hardly mean 4♣ as showing just clubs. It shows values in clubs and support for hearts.
If North passes over 4♣, East normally corrects 4♣ to 4♥. If North bids 4♠, East can compete further if holding a club fit or lead a club against 4♠ if not.