You hold: ♠ 863 ♥ 5 ♦ K73 ♣ AKQ983

Even if you like to raise partner’s major with three-card support, this is absolutely not the time. You definitely want clubs to be trumps if this turns out to be a part-score deal. You can show your spade fit if partner acts again or if the opponents balance. The club suit is the main feature of your hand here, and if I had to guess, I’d expect three no-trump would make as often as four spades even if you have a 5-3 spade fit.