Set out urn and teapot, Ma, in case (11)
I believe the answer is:
portmanteau
'case' is the definition.
(I know this)
'set out urn and teapot ma' is the wordplay.
'set out' is an anagram indicator.
'and' means one lot of letters go next to another.
'teapot'+'ma'='teapotma'
'urn' put after 'teapotma' is 'teapotmaurn'.
'teapotmaurn' is an anagram of 'PORTMANTEAU'.
'in' acts as a link.
(Other definitions for portmanteau that I've seen before include "Word such as "bromance"" , "Brunch this term" , "Large old case" , "Travelling-bag" , "said to have several uses" .)