The Playing Fields of Eton by Shackleton

Here's your chance to have your say in the UK referendum on EU membership! The wordplay in each of nine clues leads to the answer with one letter missing. You must choose these letters so as to provide support for your highlighted campaign. The Chambers Dictionary is recommended.
    1    Finish short match with clubs in draw (6)
    5    Counsel backed District Attorney’s power base (6)
    10    Vote against change in Church composition (8)
    11    Waste substance coming from old city drainage channel (4)
    12    Slave originally bound to a small plot of land (4)
    13    Ex-student closing eyes to name unknown compounds (5)
    14    Old letter from the cast (3)
    15    Soprano to join another singer in the spring (5)
    17    Sexier bust? Time to live again (7)
    18    Charlie dumped by pretty New Mexican (3)
    19    Aspen tree’s last leaves quivering in breeze (4)
    21    Injury sustained by former royal – one who’s bleeding (8)
    26    Newton abandoning high precision instrument for displaying colours (8)
    28    Son with keen resentment for father (4)
    29    Musically sustained number (3)
    31    Commando circling around in ditch (7)
    33    A week in Germany on vacation could be awkward (5)
    35    Self-confidence to travel beyond Spain (3)
    36    One creature from Disney without head and feet (5)
    37    Step aside from acting, song and dance (4)
    38    Best part of Morecambe and Wise finally making a comeback in Ireland (4)
    39    Note liberal document about green branch of technology (8)
    40    Deny getting involved with IS? That’s malicious (6)
    1    Log books aboard at all times (5)
    2    North American leader’s address overcoming resistance (7)
    3    Sex appeal joins them? (4)
    4    What could be spicily prepared topped our rice crackers (7)
    5    Formed tan, tan that is orangey (7)
    6    Did the business inside alternative house (5)
    7    Birds with special mating period, ducks all turning up (8)
    8    Kentish harbours eject Middle-Easterner (6)
    9    Asian holiday on the 3rd of June (7)
    12    Doing farm work under sun, male sloth’s no good (8)
    16    Course checked by our wingman (8)
    20    Low singer is uplifted, captivated by variegated dandelion (8)
    22    I entered into burrow and I brought up little pieces (7)
    23    Scottish area requiring compliance for right dialect (7)
    24    One doing a cracking job retires, heading off to relax (7)
    25    This requires folding dress packed by old friend (7)
    30    European songbird reared nestling with another bird (5)
    32    Little fellow eating pound of Roman brown bread (5)
    34    Dutch reserve’s throwing game (4)
Printable PDF version To enter this competition, send your entry as an image or in list format indicating the highlight , to derekharrison@yahoo.combefore the 8th July 2016. Polling will end at 10pm on 23 June. Entries after the end of polling should highlight the result but will still be eligible for the prize. The first correct entry drawn from the hat will receive a book donated by the Crossword Centre