2 down: It helps to erect vicarage minus church involvement? (6)
Yet another cheeky direct clue, with a ridiculously good anagram formation: vicarage minus church involvement = via grace minus ce involvement = via grace – ce = viagra = it helps to erect.
16 down: Cryptic end of idle boozer — idle with a capital I (8)
Very clever double use of idle: end of idle boozer — idle with a capital I = e + sot + Eric = esoteric = cryptic.
3 down: Made calls for redhead, roughly (4, 6)
I love a good piece of slang in my crossword: redhead, roughly = ranga + round = rang around = made calls.
27 across: Style of cold welcome, rejecting twit (7)
And here’s another bit of slang: cold welcome, rejecting twit = c + hi + rejecting nong = chignon = style.
20 down: Handy in ideal zoological division (6)
I thought this was a mistake before I realised the genuis: handy in ideal = h and y in plum = phylum = zoological division.
5 down: So-called goof accepts alien flag (4, 5)
Nice aural indicator and clue combination: so-called goof accepts alien = so-called blooper accepts et = blueper accepts et = blue peter = flag.
13 down: Torture those who once rated us civilly? (10)
You repeat a word enough, and sometimes it reveals hidden meanings, much like the answer to this one did when I was asking RC how it could be explained: those who once rated us civilly = water board (they issued us with rates) = waterboard = torture.