Bhāgavata-dharma means following the orders given by the Supreme Lord, Bhagavān, as stated in Bhagavad-gītā.
(Srimad Bhagavatam----6:1:41----purport).

Bhāgavata-dharma means living according to the instructions of the Supreme Personality of Godhead.
(Srimad Bhagavatam----6:1:43----purport).

One must understand one's relationship with God and then act accordingly. This is bhāgavata-dharma. Bhāgavata-dharma means bhakti-yoga.
(Srimad Bhagavatam----7:7:15----purport).

A devotee following the principles of bhāgavata-dharma feels very much obligated to the Supreme Personality of Godhead. He can understand the difference between life without bhāgavata-dharma and life with bhāgavata-dharma and thus he ever remains obliged to the Lord.
(Srimad Bhagavatam----6:16:40----purport).

Dharma not supported by the Vedas is rejected from śrīmad-bhāgavata-dharma. Bhāgavata-dharma comprises only that which is given by the Supreme Personality of Godhead. Bhāgavata-dharma is sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja: (BG 18.66) one must accept the authority of the Supreme Personality of Godhead and surrender to Him and whatever He says.
(Srimad Bhagavatam----6:1:40----purport).

One must be very meek and submissive and try to live peacefully by lending the ear to the speeches of the transcendentally self-realized soul who speaks on the message of Bhāgavata-dharma, or the religion of glorifying the Supreme Lord and His devotees. To glorify a great man is a natural instinct for living beings, but they have not learned to glorify the Lord. Perfection of life is attained simply by glorifying the Lord in association with a self-realized devotee of the Lord.
(Srimad Bhagavatam--introduction).

The word nirmalam refers to spotless dharma, spotless religion—or, in other words, bhāgavata-dharma. Ordinary ritualistic activities constitute contaminated religion, by which one benefits by developing material wealth and prosperity, but uncontaminated, pure religion consists of understanding one's relationship with God and acting accordingly, thus fulfilling the highest mission of life and returning home, back to Godhead.
(Srimad Bhagavatam----7:7:15----purport).