Weekly welcome also to Jazzy (well tried), RE (good show), ab (good parsing but where's spike? Well solved the others). GK and Ari, full house.
Thanks to all who participated. I enjoy setting 'em immensely. I'm off to the feast now. Here's my working (already well parsed).
1. homophone (say). immediately (you say this) = right off; sounds like WRITE OFF = cancel
2. Indo-European = IE; Latin not = non; yielding i(non)e = IN ONE = combined (Chambers def)
3. anag (building) of “a vicar ran as a” = CARAVANSARAI = (sometime= at some time in the past = historical) hotel for camper people (? = loosely). camper = caravan, caravan = camper (Chambers & Ox Thes’i). caravansa rai = alternative spelling of caravanserai (Chambers)
4. length (abbrev) = l; ace = a unit (Chambers chief def); l + ace = LACE = spike (as in spike/lace a drink)
5. concealed = secret; from = of; the law = police; “so far we have” = secret of police; covers up an anagram (perhaps) of “in hell” = hinell; yielding secret of polic(hinell)e = SECRET OF POLICHINELLE = something that is common knowledge (Chambers def).
I'll peek in later
Bless
John