The answer to any "Is it possible" question is almost always yes (there is a theorem by Turing which tells us the limit of what is computable, but in practice people rarely come up against that limit). It is better to rephrase this type of question to ask how to do something, rather than merely if it is possible, since that's usually what most people mean by it. It's also a good idea to list what you've already tried, and possibly why that didn't work.
You want to use the
seq-remove function. You can read the documentation for it by typing
C-h f seq-remove <RET>. You'll see that it takes a predicate function and a sequence, and returns a new sequence comprised of those elements for which the predicate function returns nil.
For the predicate, I recommend writing a lambda that calls
string-match-p. This returns true when a string matches a regular expression. Again, you can see the documentation for functions with
Putting those together, something like this ought to work:
(seq-remove (lambda (line)
(string-match-p "^\\*+ " line))
The elisp manual includes additional documentation about these topics that you might want to read, along with documentation about similar functions that you may soon need. You can open the info browser with
C-h i. You may have many info manuals installed on your computer, but you should specifically take a look at the Emacs manual and the Elisp manual. Chapters 6.1 Sequences and 34.4 Regular Expression Searching would be good places to start.