Ah, thanks Bowergirl. I hadn't realised that the whole of the clue for 6d was a definition of the answer. I understood the definition in relation to where appetisers appear but I thought that 'leading' led to the definition of the first word, and then I was looking for the 'lady to see' part for the rest of the parsing! Totally on the wrong track!
Wouldn't a clue like this usually have an exclamation or question mark at the end to indicate that the whole clue was also the definition? Or am I getting this muddled up with another kind of clue? I guess it could also be classed as a double definition?
Thanks for the 13d hint too - can't believe I missed getting that one.
And thanks to Simon for explaining 21d - makes total sense now!
Still need to solve 20a (my LOI) Someone gave a hint for it upthread, but I'm still none the wiser.