Well the Judge John Hodgman complainant has a similar pen/pencil debate and in their case the clue giver argued that since pen and pencil had different etymological origins, it should not count, which is at least a different argument. In their case the clue giver went so fair as to contact the game manufacturer who, interestingly sided with them. (Possibly due to an excess of customer service orientation.) Judge Hodgman agreed that pen and pencil are similar enough that no, one cannot be used in the clue for the other. So, the internet agrees with me.
I had once said to someone that if I could convince a certain parental unit to go on a thing called a podcast, and then agree to actually abide by said stranger's result, I would try. But neither of those things are true. But, even if I could have somehow subtly directed the family to a podcast* well, yeah. Once upon a time there was the game "Taboo". (Yes, I know it still exists. It gets less play these days in my family. It may become clear why soon.) We played it a lot. My brother is quite a bit younger, so we sometimes allowed assists if he encountered a word that he was less familiar with. I once brought my best friend to visit and we had, unsurprisingly, spent the whole long drive talking about all manner of things and we were ridiculously in sync with the extra eight hours of together time and able to offer clues like "Carrie had one" (answer: sunburn). I can no longer remember what the answer was for which my not-quite-double-digits-at-the-time brother offered "Guys like it a lot" (I think it was beer, but there was an excellent pause as much of his team clearly thought words they weren't sure they should say in front of a young child).So, I was in charge of the buzzer for a round in which the answer for the other team was "Gotham City". I buzzed when the clue giver said "city" arguing that it was part of the answer. The clue giver argued that it was not on the list of restricted terms. I argued that the answer was never listed as a restricted term, but surely you couldn't give out the answer or part of it as a clue. Suffice it to say the discussion did not go well, and resulted in a cancellation of the game for the evening. (The rules do back me up on this, which as you likely know, hardly matters after a certain level of team spirit deterioration.)
*Remember my family disagrees with books, they are not anti-fact, but they are anti-conceding arguments, and those who want to suggest I fit in, can stuff it. What? I'm kidding.