One can do anything as Whitehall diplomats essentially decline deals (15)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

One can do anything as Whitehall diplomats essentially decline deals JACK (=Whitehall, i.e. the UK actor!!) + <dipl> O <mats> (“essentially” means middle letter only) + FALL (=decline, deteriorate) + TRADES (=deals (in))