Adjusting Post Text Line Height [ie, space between lines in a para]

Hi Tom/Leo,

re - a simple one! [famous last words ;)]

Just seeking some clarification to adjust gap between lines in a text paragraph - would you mind advising if the following CSS should work please, in a post, TEXT paragraph?

.p {
line-height: XXpx;
}

Any amendments/improvements to the above code please? Thank you.