Arse-licking is the sucking-up itself — always being very nice to people in authority because you want them to like you — and it is also the rude label for a person who does that. You can talk about arse-licking as a kind of behaviour, or you can put it in front of a noun: an arse-licking email, an arse-licking colleague. Like arse-licker, it is British, vulgar, and meant to show disapproval. The picture is the same crude one. In careful or kind speech people say sucking up, playing up to the boss, or flattering. This word is the hard shove. Though actually, again, not every warm word to a person in charge deserves it. The speaker is claiming that the niceness is a tool, not a feeling.