A fanny licker is also a name for a small dog that grannies buy when their husband has long passed away, this little pooch then takes on the roll the husband used to play (in the bedroom)ie: licking grannies minge!
Grandchild: are you lonely when you go to bed nan?
Grannie: no darling, I take my little fanny licker to bed these days, he's better than grandad!
To be "sucking up" to someone which is met negatively by fellow individuals and brand you a fanny licker.
He was a right "fanny licker" with the boss today, to get a rise.