Puzzletome Crossword Puzzles

March 2019 Monthly Crossword
March

Quick march, left, right!

It will soon become apparent that a self-referential 'chain' of clues is contained in each of the left and right halves of the grid. One of the clues in each chain is suitably undefined. With reference to the grid theme, an appropriate message will appear on completion.
Grid
Across
7'Cos 24d is result (5)
8 28a regularly billed brewer for flier (9)
10 Stabbed in the heart 15a (6)
11 Nice summer after Mark has card finally swiped (8)
12 Slow to lead minor (8)
13 18d pulled back Knight to Queen 3 (4)
15 7a firm question keeping May leader (7)
17 American windbreaker without cover... he takes over (7)
20 Cut nearly all of shock (4)
22 Tuna and crab paste with ale and slice of olive (8)
25 Late rugby second row and stand off (8)
26 Generous inclusion of wine in concert (6)
27 Partner of diner by unusual display (9)
28 Contract termination applied to 13a (5)
Down
1He's learning to control yob culture (9)
2 Discover right 10a that Ulster Unionists hold (6,2)
3 Aim to get prize money in the toilet? On the contrary! (7)
4 Disguises treatment criminal boss brought about (8)
5 Opening closure? (6)
6 Create speculation inside, for example (5)
9 The real, undeniable essences! (4)
14 Producing consistent measures for underground men working around Circle (9)
16 Mocking bird finally is a corn fritter (8)
18 23d core, so return (8)
19 UK principality shortly to get ruler mobile (7)
21Organise Buffalo Bill to suppress Indiana's final frontiers? (6)
23 Several 8a computer problems (4)
24 Dogmatic 2d music (3,2)