Clark is a poet, although his work edges into the visual arts as it often appears as installations or interventions within a gallery environment, the landscape or public spaces. He began writing in the early to mid-1960s and his prose is characterised by an interest in the Scottish landscape and, in particular, the Highlands and Islands. In 1973, along with artist Laurie Clark, he set up Moschatel Press, which published works by the likes of Ian Hamilton Finlay. More recently he has used the press as a means to experiment with his own work and its relation to the printed page. Since 1986, with Laurie, he has run a project space for minimal and conceptual artists called Cairn.