Going is slow - it must be the hot weather:
28d Rest at bottom of old hill and was redeemed in Ayr (6) MO?S??
40a Edward followed back American tennis star (6) TI?D??
29a Experiences affairs without husband (6) ART?U?
27d Round about 600 yards before the priest returns (7) A??A???
16a Gaston's journal of French is withdrawn (8) ??L????E
18a Walter's angry when snack has change of rating (7) ?O?S???
Some of the clues may be thematic leading to surnames, grid entries are given names.