That Moment by Chiffchaff

In That Moment something thematic must happen to two answers to resolve four clashes in the grid. In eight across clues one letter has dropped into the next clue and needs to be restored before solving. Read in clue order these give a thematically treated word which indicates where to look next to find out what has to happen to one further answer in the grid.

    1    Formidable opponents “Très Grand” in translation (6)
    5    Intrudes before rightful heir takes possession of what might be land subsidies (6)
    11    Matted hair on male pilgrim’s clothing (5)
    13    Herd you trade in Northern Ireland for masses of tissue (7)
    15    Orang-utan almost slaughtered reactor’s financial backer (9)
    16    Cut cylindrical disc from middle of mangled sea cucumber (7)
    19    Rand one dropped from enormous Earl’s upfront payment to Jonathan (4)
    21    Copies of reflective art song including chorus originally in German (8)
    22    Very small youth getting lanky at last (5)
    23    Knight leading horse out of barn in Japanese city (4)
    25    Rent not retrospectively including what’s left owing to Rachman (4)
    27    Left throwing out last of turkey from Christmas over a month (4)
    29    Vulgar antique loo’s fashionable (4)
    30    Electronic ticket shown before opening to newest floor in the Louvre? (5)
    31    College expert going over exam material (8)
    33    Spin drier for delicates ultimately goes wrong (4)
    36    Mailers I distributed once ready in Portugal (7)
    38    One advising young Natalie not to fib indiscriminately (9, two words)
    40    Set of quadrilles – earner for the first of those taking part? (7)
    41    Without approval, look up end of yokel’s small magnifying glass (5)
    42    Cheering when shower covers husband with goo (6)
    43    Beyond revolving door, seventy-eight unoccupied sun beds (6)
    1    Pitch tent (4)
    2    Those welcoming more ecological society taking time on vacation to replace nuclear energy (8)
    3    Escort spilling bit of bilge water in Cannes (3)
    4    Check Tyson’s head following KO (5)
    6    Bankers’ chief bears annual return for university treasurers (7)
    7    Enter times incorrectly for device measuring vapour pressure (10)
    8    Local sows rolling in thistles (4)
    9    Southern Irish lake is Betjeman’s proposed bomb-site (6)
    10    Fire opals – gems with no marks enthralling drunken sailor (9)
    12    Hard outgrowth’s spine scratching head (4)
    14    Where one might keep records for a visit from a couple of eccentrics! (8)   
    17    Act parsimoniously parking in enclosure once close to Scottish island (10)
    18    Delicious food served up sustaining grey, outdated old dame (7)
    19    At last stupid, entertaining jerk gets dry wit (9, two words)
    20    No longer broods about Tax Office describing frank discussion (8, three words)
    24    Slimy old slug slithering across a wild rose, not spotted initially (8)
    26    Prohibit unruly prisoner of war cutting ropes I supply (7)   
    28    American hunter’s almost out for one in Havana? (6)
    32    Underwear that’s right for navy ship (5)
    34    Disreputable people climbing short steeple (4)
    35    Jack up Australian goods (4)
    37    Prosecutes suspect receiving ecstasy (4)
    39    Noisy group of people? Cross over (3)
To enter this competition, send your entry as an image or in list format giving the final entries to before 8th August 2022. The first correct entry drawn from the hat will receive a book from the Chambers range, which has been donated by Chambers.