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You will be struggling to find the solution to 36a if you're looking in Chambers. The preamble says it is in Collins English Dictionary (accessible on the web).
Thanks to all four!
I think I have them both, the three letter 'race' synonym I can't check as I am without my Chambers temporarily, I think maybe it's a carpentry term or something.
Full grid now. But as my MO has been to find any word that fits, with a suitable definition in the clue, I have fourteen unparsed, without extra letters, so still a lot to do!
Nearly finished, just can't see the first three letters of the profession. I have first letter as A, (which looks dodgy) then can't see the next two. So any help to parse 15a and 18a would be very welcome. I have both answers.