Since Deekay hasn't come back for nearly two hours, I'll do it properly for him/her. I'll also assume that these are the last three and give you the found letters. Also note that the last letter of 20A is the fourth letter of 17D and the penultimate letter of 23A is the sixth letter of 17D.
20A - Coat, that guy's second, shows such manliness (8) ?A?H?I???
23A - Splendid broadcast organised (9) ?R?N?I???
17D - Support European partner (7) ?S?????