Instrument in itself means flight time under instrument flight rules, not in IMC, and yes, that is usually in the airline world the while block time
ICAO Annex 1 defines "Instrument flight time" as " Time during which a pilot is piloting an aircraft solely by reference to instruments and without external reference points". EASA on the other hand has a slightly different wording, but the intent is the exact same, "means the time during which a pilot is controlling an aircraft in flight solely by reference to instruments". FL370 IFR plan and gin clear day doesn't make the cut.