A quick google for 'Mead ingredient "pinks"', turns up lots of references to Dianthus gratianopolitanus aka Clove Pinks aka Cheddar Pinks and sometimes called GillyFlower.
It seems it was commonly used to flavor wines and other drinks since medieval times.
The flower and parts of the stem have a clover-like flavor.
It also seems to turn up in relation to harry potter, please tell me that's not where your recipe is from.