Use &pattern command within less.
From the man page for less
&pattern
Display only lines which match the pattern; lines which do not match the pattern are not displayed. If pattern is empty (if you type & immediately followed by ENTER), any filtering is turned off, and all lines are displayed. While filtering is in effect, an ampersand is displayed at the beginning of the prompt, as a reminder that some lines in the file may be hidden. Certain characters are special as in the / command: ^N or ! Display only lines which do NOT match the pattern. ^R Don't interpret regular expression metacharacters; that is, do a simple textual comparison.