Clue: Playing whist, void of hearts, trump's opening: another card, please (5)
Answer: TWIST
Explanation: Definition: another card, please
An anagram ('playing') of 'w[h]ist minus the H ('void of hearts') plus T ('**T**rump's opening'). I learn that only in the British version of the card game twenty-one, called pontoon, is TWIST used to request another card.