Use one, about to dish up outside (7)
I believe the answer is:
service
'use' is the definition.
(thesaurus)
'one about to dish up outside' is the wordplay.
'one' becomes 'i' (Roman numeral).
'about' becomes 'c' (circa abbreviation).
'to dish up' becomes 'serve' (synonyms).
'outside' is an insertion indicator.
'i'+'c'='ic'
'ic' going inside 'serve' is 'SERVICE'.
(Other definitions for service that I've seen before include "Work done for others" , "tree" , "army, say" , "Armed force - assistance" , "Periodic car maintenance" .)