16 across: Virgin precaution [that’s how it reads] linked to degree in weight? (7)
Great definition: that’s how it reads linked to degree in weight = SIC linked to BA in KG = SICKBAG = Virgin precaution.
21 down: Copied clothing? May initially be charged in Gen-Y vein (5)
I liked the slang, but even more so I liked the punctuation that led me astray: copied clothing? may initially = APED clothing M = AMPED = be charged in Gen-Y vein.
2 down: Brilliant 24-across (portmanteau) unchanged by pest extermination (11)
Freakin’ genius: portmanteau unchanged by pest extermination = FANTABULOUS (fantabulous – ant = fabulous = fantabulous) = brilliant.
27 across: Hippie’s advice to enjoy number? (5)
I spent a while thinking DA was being tricky and meant number in the sense of something that numbs. I should have concentrated on the simpler option from the start, which also turns out to be amusing: hippie’s advice to enjoy = DIG IT = DIGIT = number.
17 down: Rumpus room using Titanic 24-across (portmanteau) (9)
Just when you might have thought you’ve read all possible anagram indicators, out comes DA with the inspired rumpus. Like this: rumpus room using = GINORMOUS = Titanic portmanteau.
19 down: Faux pas cryptically close to dropping a beer (7)
Features one of those delightful tricks that is almost impossible to work out before the answer becomes apparent: faux pas cryptically close to dropping a = SLIP UP cryptically NEAR dropping A = PILS NER = PILSNER = beer.