What I remember is that it was on ao3, Clint is transformed into a dog, and left for a while with a dog handler? Someone who doesn't know about the transformation anyway. It was either clint/coulson or gen with c/c feels. I searched the tags on ao3 but only found fluffy corgi!clint, I remember this as being more angsty and no corgi.
Please please for the love of ice cream help me find this fic! Or I'll have to assume it was a figment of my imagination.
ETA I love this fandom. Found in record time - Pedigree