1d Doctor uncovered hellish yarns (6) AISL?S looks like aisles ? Misprint ?Missing letter ?
23a Seaweed entangles navy diver (4) H?NE
12d Small traveller blocks group of motorists (5) AR?SA
28d Heard to be sad in part of the day (4) ?OPN
1d - Anagram of (h)ellis(h) + unclued letter
23a - A word for seaweed round N for navy - clash in first letter and a misprint
12d - AA round a word for a traveller - S clashes
28d - First part of day sounds like a word meaning to be sad - clash with P