Brother of Walter Clagget. About 1760 he published music with Walter in Edinburgh.

Barlow states (without citation) that Clagget 'alongside his work inventing and patenting musical inventions ran a music shop'.

Dublin agent for James Watt (1763-1819) from 1763, purchasing 'mostly guitars (presumably of the English type) made by Watt's employee Robert Allan (Holman).

Partnered with William Gibson as Clagget & Gibson until c.1764: a letter in Clagget's own hand (extant in Birmingham City Library Archives, transcribed and published by Barlow) states that the partnership ended 'above a year since' 1765.

After the Gibson partnership ended, Clagget wrote to Watt suggesting a partnership and offering 'to explain all the improvements that Gibson had made to guitars'. This partnership did not materialise (Holman).