Assuming these are correct, I would appreciate help with the parsing, thanks...
12a Runner arrives in haste at start of relay (7) - HARRIER
If the definition is "runner" and the final R is from the start of R(elay), then "harrie" must come from "arrives in haste" but I can't find that word anywhere.
24a Defector from Scottish party returning her dress? (6) - TARTAN
56a "Where is the college porter?" barmaid said (4,6) - BEER CELLAR
I get that "porter" is beer but what is the "college/cellar" part?
57a Setter chosen - assess regullarly for brevity (9) - TERSENESS
It looks like (set)TER + (cho)SEN + (ass)ESS, but it says 'regularly' which usually means ever alternate letter - in this case, how can it mean 'the last half' of each word?
37d Inch round close to blue delta, not across the bay? (4-6) - SIDE SADDLE
I get the cryptic definition (not across the bay/horse), and assume "inch" = SIDLE and "blue" = SAD, but how does the rest come from "delta"?