How to clarify what you mean by "Standard Time" in relation to time zones?

The phrase Pacific Standard Time (PST) is not ambiguous when used correctly: it stands for UTC-8 (or GMT-8), i.e. for the first of the two alternatives in the question.

The term for the second of the two alternatives in the question is Pacific Time (PT), or the time in the Pacific Time Zone. One can also say 'the local time', if the context makes it clear what the location is, or something like 'when it's five o'clock in Los Angeles'. All of them unambiguously stand for whichever of PST or PDT is observed on the relevant day.

Now, it is true that people sometimes use PST when they, in fact, mean PT, probably in a misguided attempt to sound more official. That mistake is sufficiently widespread that the phrase may occasionally be confusing in practice, so it is understandable that the OP is reluctant to use it. Fortunately, the phrase is easy to avoid, as in day-to-day life, one very rarely needs it, because one almost never refers to PST for the part of the year in which it is not actually observed (and for the part of the year in which it is observed, there is no difference between it and PT).

While you, your organization, or localized figures of speech are free to establish whatever convention you care to, there exists an international voluntary standards organization that has addressed this question in a published standard, ISO-8601

This ISO standard helps remove doubts that can result from the various day–date conventions, cultures and time zones that impact a global operation. It gives a way of presenting dates and times that is clearly defined and understandable to both people and machines.

I understand the present conventional meaning of "Pacific Standard Time" as the time in certain US Pacific states when daylight savings time is not in effect. The unambiguous way to describe this is by an offset to Coordinated Universal Time (UTC), rendered as "UTC-08:00". While the actual standard is behind a paywall, the functional information is reproduced on Wikipedia.