Across

1 Serious one with directions to perform marriage (9) SOLEMNISE [SOLEMN(Serious) + I (One) + SE(Directions)]

5 Apprehensions about an unsafe arsenal in part (5) FEARS [Hidden Clue - unsaFE ARSenal]

8 Move tire around after regular work hours (8) OVERTIME [Anag of MOVE TIRE]

9 A small street branching off another (2-4) BY-LANE [Direct Clue]

11 Player getting some factorage (5) ACTOR [Hidden Clue - fACTORage]

12 Announcement breaking into a TV programme: "All points break into flame" (9) FLASHNEWS [FLASH is flame, all points is NEWS]

13 Soldier in cavalry regiment, American in reckless retreat (6) HUSSAR [American is US and RASH is reckless, retreat makes it HSAR]

14 Appoint an amusing person as a carrier of a short letter (8) POSTCARD [Not very sure about the explanation]

16 Zero hour? (8) MIDNIGHT [Direct Clue]

18 Bloodsucker, irritant for one retired (6) BEDBUG [Direct Clue]

22 One going back on promise with muscle (9) RETRACTOR [Explanation Please??]

23 Article yielded by plant with thick fleshy leaves (5) AGAVE [A is an Article, Yielded is GAVE]

24 Some food at a time of fast to begin with (6) LENTIL?? [Not too sure]

25 Device for hauling things up is a breeze on the French vessel (8) WINDLASS [Wind is breeze]

26 Bundle of yarn, note, found wrapped in hide (5) SKEIN [Explanation please??]

27 Itinerant salesman (9) TRAVELLER [Direct Clue]

Down

1 Bread basket (7) STOMACH [Fits there]

2 One of the Bard's characters who relates differently (7) LAERTES [Explanation please??]

3 Liaison — a matter I spell out, conjuring up a spirit (15) MATERIALISATION [Anag pf A MATTER I SPELL OUT]

4 Protected against disease by one measure, French one (6) IMMUNO [I(One) MM(Measure) UNO(French One)]

5 Suddenly become very angry and offend hefty Hall shockingly (3,3,3,6) FLY OFF THE HANDLE [Anag of AND OFFEND HEFTY HALL]

6 American state degree accepted by a monk (7) ALABAMA [A la BA ma]

7 Boiled article with egg all around (7) SEETHED [Not too sure]

10 In a little while, swallowing a drop of whiskey, lose consciousness (5) SWOON [In a little while is SOON and drop of whiskey is W]

15 Chess player who mixed with leader of ecologists (5) P[]

16 Game with little glass balls; lose them and go mad (7) MARBLES [Direct Clue??]

17 Tenet Ed formulated for easing of tension (7) DETENTE [Anag of TENET ED]

19 Hand tool gets a plug in a fracas (7) P[]

20 He reduces friction, applying oil (7) GREASER [Direct Clue]

21 Treated air can be a medicine for bruises (6) ARNICA [Anag of AIR CAN]