Schoolboy Howler by Hysterix

Clues are presented in symmetrical pairs; the two clues in each pair stand side by side without overlapping and either may appear first. Central row and central column are unclued. One letter is to be omitted from the answer to each clue and entered into its numbered square outside of the main diagram. Definitions refer to the full word, subsidiary indications to the form entered into the diagram. The SCHOOLBOY HOWLER (14 words) will appear in the top, central and bottom rows, followed by the left, central and right columns. Use Chambers (1998).

ACROSS
1:36 Paddy to ridicule strike about Poet's ground (4:4)
5:35 With Arabs supplying instrument, one within struck with a sword (7:7)
10:34 A back pain warning Tina to adjust things (5:5)
11:33 Small child to join in correcting page on the right? (5:5)
12:32 System of recording melting-point briefly examined, Scots chill nothing before one (5:5)
13:30 Name and address over gateway faces a queen? (5:5)
14:27 To crush American mixed grain Scottish concern works to rule (7:7)
15:25 Plant support left in country ditch to give way as before (6:6)
18:24 A mug, beginning to speak with difficulty about linked verse, rang off (5:5)
19:23 Jock's pet beetles get disheartened after returning in darkness (5:5)
DOWN
1:22 Argument Queen mounted to impede awfully large European majority (7:7)
2:21 Deposits without limit on a road greeting everyone with trouble (7:7 hyphenated)
3:29 In or out, all the birds name parliamentarian with hospital maiden (5:5)
4:28 The conclusion of some American nonsense on English marching orders (5:5)
6:20 Three in Italian repeating ending of another story in Greek book (7:7)
7:31 One beginning to devise a plan to stick old wood (4:4)
8:26 Disorderly one to scratch at Troon? A tell-tale English yarn! (4:4)
9:23 Date change - one particular worker given about two seconds to agree (6:6)
16:17 Heather to launch ship laden with Irish elders (5:5)
18:19 Eastern drama, a star born among Saints falls from grace (4:4)