Panacea by Sancho

Six unclued lights are of a kind.  Given their location within a 14 x 14 receptacle – and to some degree, the name of their kind - these lights could well have a feature that is formed by the two remaining unclued lights. Wordplay in across clues gives the answer plus an extra letter, apart from one clue which contains an extra word in the definition part. Read in clue order, these letters, and word, give a revealing instruction.

1    King’s heart removed by head of cardiology quack (6)
5    Billy Connolly’s type embracing right hand man (3)
7    Textile qualification taken in three years (5)
11    Incense constituent of Big Apple with empty-headed answer (6)
13    Paragon of a native? (5)
14    Master of getting money sponging about (5)
17    Tree surgeon lopped off more – fussy (5)
18    We keep cool in cow shed (7)
23    Clear 6! Old Max finishes with 80 runs in the bag (6)
26    Telltale evidence buried by dissolving it in acid (7)
28    Sopranos hold key after wide, vacillating variations in pitch (6)
31    Writer’s goddess to ditch provincial version of Villette’s ending (6)
34    What Cousteau got into perhaps on clammy Society night in Paris (7)
36     Net adrift astern (5)
38    Emphasised again care for needy; rudely not accepted (10)
39    More than one hyphen requirement in edited scene for example (7)
40    Salmon found in North Korea, perhaps (5)
41    Scott’s mate returned Newton’s marble collection (5)
42    Wisecrack leading to embarrassment after evening do (6)
43    Sense hawk circling mount (5)
44    Pen Highland cattle by borders of wold (3)
45    American army shadowing most of X men mutants(6)

3    Time’s flying - cagey relatives avoid him locally for ages (6)
4    Bone needs setting in governor’s arm (7)
5    Hal’s bar at Worthing, ‘A Bounteous Bottle’ (9)
6    Cambodian rhino spotted in safari elsewhere (5)
7    One new angel administered anointing in extremis (7)
8    Introductory sections in the manner of a postscript (6)
9    Defence so neglected to press last of witnesses, he finally broke and... (9)
10    Sailors bound south in subdued spirits (8)
12    Number 17’s more fragrant (6)
19    Pasty: pie crust with a liberal filling (4)
22    ‘Listen once more’, said Said, and said it again (9)
23    That which is seen’s inferior to that which is not seen, poetically speaking (8)
24    Catches eel on the way back (4)
27    Jaguar nearly driven through middle of precinct; learner joining steering group (7)
28    Retires finally in dignified step down (7)
29    Having abandoned Grail chasing, saint nipping off to McDonald’s to eat like a pig (6)
30    Journalist’s something of verslibriste élégant (6)
32    ‘Close to the last of the moola, sugar’; ‘Then make more, darling’ (6)
33    Stood in Globe, fan acclaims something delivered during Twelfth Night (6)
35    Forward roll on axis (5)
To enter this competition, send your entry as an image or in list format with a description of the final grid, to before the 8th November 2013.  The first correct entry drawn from the hat will receive a copy of one of the range of books which has been donated by Chambers.