ACROSS

 1  Could be either I or Adam! (5,6)

 9  Placed in one which should be really progressive, but I’m using it right now! (8)

10  Didn’t bid with what you hear if over. (6)

11  To be made up of what is continued shortly about a diminutive nun. (7)

12  In an outstanding way, sort of angry about couple of numbers from old Rome. (7)

14  Rolls here, for example. (6)

15  It’s an awful sin to take such wild rides, but such should be pretty hip, usually! (8)

17  Serf’s hen, twitchy, brightens things up. (8)

20  A large number to put on a show with you and me, but it’s bound to have its sticking points! (6)

22  Scans around what would be great, in modern terms, and talks too! (7)

24  Not Miss Muffet’s favorites! (7)

26  Put two and two together again, to fix things up! (6)

27  Tenure is, perhaps, with lots of followers. (8)

28  He directs customers, but the insomniac might be one, too. (11)

DOWN

 2  They’re not who they claim to be–the little devil so “up,” what’s left is a mess! (9)

 3  Say about what might be found in the velvet glove, turned to give enough. (7)

 4  Carefully examine the twisted rope! (4)

 5  The man who takes things back (rats! one-fourth gone!) gives an account. (7)

 6 ” Well, well, well,” says a well-known director! (5)

 7  Obviously, Rambo got arthritis in South America! (6)

 8  One of those found at the banks is let up on the French capital of Rouen. (6)

13  Run water over a nervous siren! (5)

16  Degeneracy starts this month on a study on the Common Era. (9)

18  The door opened up around E.T., dizzy and unable to move. (6)

19  Grab ’em! O, chaos! There’s no entrance or exit with it. (7)

20  Great! Cal eats Middle Eastern bread. (7)

21  Sounds imaginary, but the kite flier and the projectionist do it. (6)

23  If you don’t succeed, adding fifty will only cause you to thrash about. (5)

25  Boast is a common start to a quarrel. (4)