Hi Anne , Castletown is in Kirk (County) Malew , so the IGI Family search has two possibilities :

Ch Malew 29/5/1803 Elinor Clucas , to Thomas Clucas and Elinor Clague and

Ch Malew 21/10/1804 Elinor Clucas to William Clucas and Elizabeth Cowel ( can be Cowle, Cowell)

William Clucas married Elizabeth Cowle , Kirk Santon ( County 8 kms from Malew) 26/10/1793

Can't find marriage of Thomas and Ellinor Clague , but there is a marriage of Thomas Clucas to Ellinor Scott 19/8/1801 in Malew , and a marriage of Ellinor Clague to William Scot 14/12/1794 in Malew , but can't find a death of a William Scott 1794-1801.

The Manx had a strong tradition of naming children , First son after Father's Father , second after Mother's Father , first daughter after Mother;s Mother , second Father's Mother , so if you know the names of all William Hughes and Eleanor Clucas , you should be able to trace which one of the two possibilities..

My wife was a Clucas , her grandparents born on the IOM

Cheers
David Dwyer
Sydney , NSW