The Debian packaging of clojure-mode is maintained in git, using the merging
workflow described in dgit-maint-merge(7).  There isn't a patch queue that can
be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For example, to see
the changes made by the Debian maintainer in the first upload of upstream
version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/clojure-mode
    % cd clojure-mode
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone clojure-mode`, rather than plain `git
clone`.)

A single combined diff, containing all the changes, follows.
--- clojure-mode-5.18.1.orig/test/clojure-mode-font-lock-test.el
+++ clojure-mode-5.18.1/test/clojure-mode-font-lock-test.el
@@ -1,5 +1,4 @@
-;;; clojure-mode-font-lock-test.el --- Clojure Mode: Font lock test suite
-;; -*- lexical-binding: t; -*-
+;;; clojure-mode-font-lock-test.el --- Clojure Mode: Font lock test suite -*- lexical-binding: t; -*-
 
 ;; Copyright (C) 2014-2021 Bozhidar Batsov <bozhidar@batsov.dev>
 
