Thanks smithsax/adeano -- yes, I think I can see that a thrower of those things could arguably be a prankster. However, I'm not sure the BRB includes a thrower as one of the meanings for that word, so I guess that becomes my quibble...! Likewise with the gratitude for "you shouldn't have" -- I don't think that's shown in my BRB either, or at least I haven't found it. Now, I realise that Chambers is the "primary reference" and not the exclusive reference, but definitions that fall outside it are normally called out in the preamble.
Speaking of the preamble, I'm afraid I do take issue with it on two
other points. First, I can find in the completed grid at least *three* separate sets of "4 cells in a straight line" that spell the product. Including the word "contiguous" would have made that unambiguous, I think, and I imagine it is that set that was intended -- that's certainly the set I highlighted. Second, I am less forgiving than smithsax@50 -- eleven of the down clues have a relationship with their grid entries that is not signalled in the preamble except by the quasi-hint of the inclusion of the phrase about numbers in brackets as I mentioned in my earlier post. I love engaging with tough clues, struggling to spot and apply a theme, addressing the other features the preamble sets out, and completing a tricky endgame, but I do not enjoy having to second-guess a sloppy or incomplete preamble, and I think if answers need to be modified or trimmed or spaces left when entering into the grid this should be at least hinted it in the preamble.
But those are just minor niggles with an otherwise enjoyably challenging puzzle, so I'll shut up now :-)