Fury assigns Clint from Coulson to a new handler. The new handler had been Loki's, who flipped out and left the Avengers without explaining why. Fury suspects the handler is the reason & figures Clint won't take any crap & they'll get the truth about the handler from him. They thought wrong. Clint allows the handler to physically & emotionally abuse him, due to a misunderstanding of the handler/asset guidebook.
Features Clint using the air ducts to sneak into Coulson's room to sleep on his couch, until he gets the new handler who punishes him for it. Loki eventually returns to warn Clint, then Phil & the team find out what's been happening & much badassery ensues on behalf of Loki & Clint by their team.
Can't remember if it ends with Clint/Coulson or if it's only implied. I think there may have been implied (strongly) Natasha/Fury, but nothing explicit.
FOUND, no longer on-line, but PDF copy provided by other member. Thanks tamnation!