Thanks for your replies - makes it clearer for me!!
Strange thing is - one of the times I've heard the expression used doesn't really fit in with the above explanations. I was talking to a YO about a year ago and she knew of a horse that my friend used to own before she sold him on. The horse ended up at the YO's stables but the new owner neglected him badly which resulted in the horse becoming very ill. The YO said she eventually rang the owner and told her that if she didn't come and sort out her horse and get it PTS she was going to "drop it off at the hunt". She said that the owner then took the horse to a new livery yard so she wasn't sure what happened to it after that.
At the time I was trying to appear as knowledgeable as poss (I was scoping the place, whilst thinking of buying a horse to stable there) so I didn't ask her what she meant.
Apologies for being thick (again!
) but what did she mean? Did she mean she would take the horse while it was still alive?