Yes and no,
Your example is:
font-family: 'Montserrat', Light Italic;
The Google font weight 'light' is weight 300 (for italic or normal font-style). And also in CSS font-weight: normal is equivelent to font-weight: 400, and bold is equivelent to 700.
So that allows us to get close using the font shorthand syntax which allows a number of font properties such as the font-style, font-weight and font-family you want to be declared in one go.
Unfortunately, the font-size value is a requirement of the font shorthand syntax so you'll need that in there too:
font: italic normal 1rem 'monserrat'
or
font: italic 300 1rem 'monserrat'
The second one there gets you the equivalent of the 'Light' font-weight but 'Light' isn't a valid CSS font-weight - 'normal' and 'bold' are along with a few relative terms as well such as 'lighter' or 'bolder'.
You could also use initial or inherit as possible values for the font-size.
You can use that style inline.
<p style="font: italic 300 1rem 'monserrat'">...</p>
Not quite what you were after? But as close as you will get :)
More about font shorthand:
https://css-tricks.com/snippets/css/font-shorthand/
https://www.impressivewebs.com/css-font-shorthand-property-cheat-sheet/
And an additional point - each of the styles you include in your import rule add to the load time and bulk of your page, it's probably a good idea to identify which you will use and only include those. For example, if you don't need a 700 weight italic font, don't include the 700i in your import
font-family: 'Montserrat Light Italic'? No, that won't work, because the Google style sheet does not "register" them under that identifier, but uses the same one for all versions - and that is usually what you want, so that by just specifying that general font family, the browser can pick the appropriate style based on the font-style and font-weight. - CBroefont-weightandfont-style? That’s exactly what they’re for. - Ry-