His other stage work includes Hamlet and Polonius in Hamlet, Macbeth and Marcellus in Macbeth, Salerio in The Merchant of Venice, Thomas Becket in Murder in the Cathedral, Eilif in Mother Courage and Her Children, Roat in Wait Until Dark, Estragon in Waiting for Godot, in Romeo and Juliet, King Henry II in Becket, Ebenezer Scrooge in the musical Scrooge, Henry VIII in A Man for All Seasons, Bill Sikes in Oliver!, First Voice Narrator in Under Milkwood, Athos in The Three Musketeers, Long John Silver in The Secret of Treasure Island, Robert Folliett in The Shaughraun, and the Spirit of Christmas to Come in A Christmas Carol.

Clarkin's television work includes The Bill in 1989, Love Hurts as Toyne in 1993, Moonfleet as Revenue Man in 1984, "Wild Rover" (Tim Cullen) 1992, Brookside (Police Sergeant) (1995), McCallum Paul O Connor Sweet Innocent 1995, The Professionals (Empire Society Thug)(1977), Return of the Saint (Guest Author at Book Launch) (1978), The Fear (1988), The Bill (Creasy) Fast Food 1993, This is your Life Todd Carty 2000 (BBC).

Narration work also includes the story of the London Symphony Orchestra and their move from the Barbican to the renovated church St Luke for BBC Four television.

Clarkin's film work includes Holocaust 2000 (1977), Force 10 from Navarone (1978), The Great Train Robbery (1979), Murder by Decree (1979), Hanover Street (1979), S.O.S Titanic (1979), Star Wars: Episode V – The Empire Strikes Back (1980), Rough Cut (1980) and The Elephant Man (1980).

Clarkin was the voice of the Victorian explorer Richard Francis Burton for the Channel 4 documentary Source of the White Nile]from the television series To the Ends of the Earth for BBC TV.