Before:
The debrief is done: Natasha will go to Russia, alone, and Clint will babysit the scientist that poke the Tesseract and Phil will keep the base in New Mexico running smoothly while Hill and Fury are in New York and on the Helicarrier respectively.
"Barton", Phil says warningly as he throws an arm over Phil's shoulders. There's no one else in this room so Clint just grins and says, "For good luck, sir."
Phil sighs into the kiss but pulls him closer anyway.
"Knew you can't resist me", Clint grins smugly and licks his lips.
"Never pretended I did", Phil counters and kisses him again and it's all deep and close and familiar.
"How much luck do you need on this mission, sir?" Clint asks when they break for air but still wrapped around each other. Usually it's just a short kiss but when it's like this there's a chance that Clint can persuade Phil into taking a long lunch break. Or rather it's a sign that Phil wants to be persuaded.
"More than I have time for right now", Phil replies with a hint of regretfulness.
"Lunch break starts in two hours" Clint reminds him with another kiss. They're slowly, unwillingly disentangle but Phil pulls him close one last time, one hand already on the door handle.
"Good luck, Agent Barton."
"You, too, sir."
Now:
Barton has the two men that will come with him ready and Loki smiles, already in his disguise.
"I'll give you the distraction you need." He will enjoy himself.
The men are occupied as they always are since Loki brought them here but Barton unexpectedly throws an arm over Loki's shoulders and leans in to kiss him.
"I never ordered you to kiss me", Loki says bemusedly once they break apart. Barton is still so close that Loki can feel his words on his skin when he says, "For good luck, sir." In such a sultry voice that in unleashes an unexpected arousal in Loki's stomach.
"And what else do you do for luck, Agent Barton?" He asks intrigued.
Barton gives him a filthy grin and Loki is a little more than intrigued.
"That depends how much time we have, sir."
"I'll make time"; Loki assures him and Barton's hand is on his neck pulling him in and the intent of this kiss is so clear that it makes Loki's knees go weak.
Then:
Natasha breaks the spell Loki has on him and Clint swears to put an arrow into Loki's eye. She's so angry she's almost trembling with it and Clint can understand that.
Loki compromised him way beyond turning him against Shield. He took something that is Phil's and only Phil's. Because that was their first kiss: a quick peck for luck in the middle of a risky mission while they were shot at and before Clint attempted something reckless to save them.
So when Captain America asks them to follow him into battle against Loki the answer is there before he even asked.
Clint takes time to climb into medical and visit Phil who's still unconscious but he'll live even if no one but a handful people know that. Fury knows better than to keep him and Natasha away from Phil.
Loki will pay for what he did to Phil, to Natasha and to Clint.
"New mission, sir", Clint says and tries to sound as if this is a normal post-debriefing encounter between him and Phil. He leans down and presses a kiss to Phil's lips.
"For good luck, sir."