New business premises ultimately ruined is uninsured: trial ensuing (7,8)
I believe the answer is:
sunrise industry
'new business' is the definition.
(I've seen this before)
'premises ultimately ruined is uninsured trial ensuing' is the wordplay.
'ultimately' suggests the final letters.
'ruined' indicates an anagram.
'trial' becomes 'try'.
'ensuing' means one lot of letters go next to another (ensue can mean to follow).
The last letter of 'premises' is 's'.
'is'+'uninsured'='isuninsured'
'isuninsured' is an anagram of 'unriseindus'.
's'+'unriseindus'+'try'='SUNRISE INDUSTRY'
(Other definitions for sunrise industry that I've seen before include "business unsuitable for setter?" , "New business" .)