KGB, say, saving Philby time, which is most revealing (9)

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

[ SPIES(examples of which are/say, members of the KGB in the former Soviet Union) containing ( saving ) KIM(Philby, once a British spy, and, a double agent for the Soviet Union) ] + T(abbrev. for “time”).