I have the answers to the last two clues but cannot parse them :
15 Down - Transcend. Clue : Trump controlled South Carolina in move. (I understand the answer means move and that South Carolina is obviously SC but the rest...?)
23 Across - Unscramble. Clue : Decode signal to stop pilots dashing for planes in wartime. (I understand the answer is "Decode Signal" but cannot parse it!)