Facilities I illuminated in redesigned suite (9)
I believe the answer is:
utilities
'facilities' is the definition.
(utility is a kind of facility)
'i illuminated in redesigned suite' is the wordplay.
'illuminated' becomes 'lit' (synonyms).
'in' means one lot of letters goes inside another.
'redesigned' indicates an anagram.
'i'+'lit'='ilit'
'suite' with letters rearranged gives 'uties'.
'ilit' placed into 'uties' is 'UTILITIES'.
(Other definitions for utilities that I've seen before include "Gas, electricity, water, etc" , "Pieces of software" , "Useful things, like gas or electricity companies" .)