Successfully picked up my friend.
Tony (succinct), AB (detailed) and Ari, all with a full house. Thanks also to RE, GK and Jazzy for some very good efforts. I'll stick my working in, on the off-chance that a beginner might find it helpful. There's no need as the parsing was spot-on.
1. anag(re-positioned) of “Vault Merlin” = INTERVALLUM = between the ramparts (Chambers)
2. take advantage of = milk; race = run; MILK RUN = an uneventful journey {US sl} Chambers
3. popular = in; male superintendant = foreman; loses heart = forman; leading tong = t; yielding INFORMANT = supplier of dope
4. Beetle, for example = car; bony extremities = by; yielding CARBY (Aust) = short for carburettor. (The “?” is because “hood” is a N. American term not Aussie)
5. tilts without using jack = (j)ousts = OUSTS = topples
Thanks again for the nice welcome. Hope to see you in a week on 5.
John