It's a winteriron fic with maybe him first being the asset....maybe at least he has decided that protection of Tony is paramount.
The only scene I remember is that Bucky tries to stop Tony from collapsing on Natasha on the couch. Natasha is having a serious bad days and pulls out a knife against Bucky. Natasha actually let's Tony tiredly take the knife and replaces it with a brand new bigger and better knife.
Hopefully that's a good enough description. All thanks in advance.