FamilySearch has Clarissa as a widow in the 1881 census - is that where you were looking?
Clarissa CAIN Head W Female 40 Douglas, Isle of Man, England Annuitant
Ann S. CAIN Daur U Female 24 Port Erin, Isle of Man, England
Edith E. CAIN Daur U Female 17 Castletown, Isle of Man, England Servant At Home
William T. CAIN Son U Male 21 Castletown, Isle of Man, England Plumber
Samuel CAIN Son U Male 18 Castletown, Isle of Man, England
Source Information:
Dwelling 17 Church Street
Census Place Onchan, Isle of Man, Isle of Man
Family History Library Film 1342346
Public Records Office Reference RG11
Piece / Folio 5603 / 29
Page Number 16

Brian Lawson's census index for 1871 has:
CAIN Clarissa 33 Cas 5777 189 15
with a Charles Cain under the same ref:
CAIN Charles 44 Cas 5777 189 15
www.iomfhs.im/lawsons/census/c71-ca.html

Looking between 1871 and 1881, Brian's burial index has:
CAIN, Charles Shuttleworth 47 Bra 18 Feb 1879.
www.iomfhs.im/lawsons/burials/cain_a.html

The 1871 census, ref above, has Charles S Cain, Mar, 44, Draper, b.Castletown, and Clarissa 33 Drapers wife, with their children:
Anne S Cain 14
Charles J Cain 12
Thomas Cain 10
Samuel Cain 7
Edith E Cain 6

The IGI has an extracted record (from the par reg) for Edith Elizabeth Birth: 28 AUG 1864,
Christening: 01 FEB 1865 Saint Marys, Castletown, Father: CHARLES SHUTTLEWORTH CAIN, Mother: CLARISSA, plus the other children.
If you look up the entries in the parish register it should confirm father's occupation and give other details. See the par reg at the Manx Museum Library or through any LDS Family History Centre:
Parish register transcripts FHL BRITISH Film 106193 Item 2: Church of England. St. Mary's Church (Castletown, Isle of Man) 1849-1883

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