Can't define "kink"? Perhaps people can, perhaps not.
But we live in a society which can't even define "woman" now - and the definition of "trans" has morphed from someone who has a deep discomfort with their sexed body, and needs to change it, into someone who says they are the opposite sex because they "feel" that they are.
Many of these are men whose "distress" with their sexed body it so great that they keep their genitalia which they redefine as a "lady penis". Some are women who hate being female so much that they intentionally get pregnant and have babies while continuing to take testosterone - and who knows what effects this may have on a developing foetus?
Some individuals swap backwards and forwards between genders as it suits them. And the recent conflation of "sex", which is observable, biological, and immutable, with "gender" which is society's expectation of typical behaviour of members of a particular sex, which constantly changes, which varies culturally, and which can't be observed, has caused many problems.
Sex is NOT gender.
No-one changes sex. Ever.
Prude as I am, I may not be able to define "kink" in a way that would satisfy you, but I can recognise fetishism. If people want to indulge in "kinks" or "fetishes", that's their choice as long as they do it with other consenting human adults in private. When people's private practices intrude onto other people's lives, and into the pubic arena, particularly when there are children present, then that is inappropriate.