Nice puzzle.
Is 9A one of the clues that needs 'consideration'?
I can see a possibility, but if it is I find it hard to parse the answer (which I have got).
Sorry nelson, mind elsewhere, Royal Ascot. I meant to say "obviously now" with the part word you had considered in full being the subtraction indicator.
I have a full grid with the relevant callers highlighted but i seem to have completely bypassed "in 6 clues, 1a needs consideration" - what have I missed?