The phrase "a adherent of" is not correct in written English.
It should be "an adherent of" due to the vowel sound that follows the article. You can use it when referring to someone who supports or follows a particular belief, ideology, or movement.
Example: "She is an adherent of environmental conservation and actively participates in local clean-up efforts."
Alternatives: "a supporter of" or "a follower of".
At the fringes, that makes him vulnerable to conspiratorial slanders: he is a socialist, a foreign imposter, a jihadist, an adherent of black liberation theology.
The adult in Season of the Rainbirds who destroys children's playthings as idols, was based on a maternal uncle, an adherent of a "strict, unsmiling sect" of Islam, who smashed his nephew's toys.
At times, it seems as though he's debating children, like a modern astronomer arguing with an adherent of a Ptolemaic solar system.
Like his brother, who was arrested during the manhunt, Merah has a criminal record including a violent crime, and is said to be an adherent of Salafism, a fundamentalist branch of Islam.
To assume that an adherent of an Islamist world view is necessarily a violence-prone, terrorist-in-waiting is not only unhelpful but seriously harmful to our understanding of the issues.
The Gospel of Judas was likely compiled by an adherent of a Gnostic sect.
He is an adherent of a Japanese management philosophy called kaizen, in which improvement is made in small increments, as opposed to the more Western approach of merging and acquiring.
Seyed Khalil was an adherent of a Sufi movement with many members, but about which little is publically known -- the Ahl-e Haqq or People of Truth, who claim millions of "hidden" acolytes in Iran and Iraq, especially among Kurds.
Mr. Sayyaf is an adherent of Wahhabism, a strict form of Islam, and a member of the Northern Alliance, whose forces were blamed for rights abuses in earlier wars.
He was never a religious nationalist, or an adherent of the "Land of Israel" ideology that viewed the West Bank as the Jews' biblical legacy.
