Useful doctor left café plugged by university (9)
I believe the answer is:
effectual
'useful' is the definition.
(thesaurus)
'doctor left cafe plugged by university' is the wordplay.
'doctor' is an anagram indicator.
'plugged by' indicates putting letters inside (plug can mean to block up a gap).
'university' becomes 'U' (abbreviation as in UMass).
'left'+'cafe'='leftcafe'
'leftcafe' with letters rearranged gives 'effectal'.
'effectal' placed around 'u' is 'EFFECTUAL'.
(Other definitions for effectual that I've seen before include "Producing the desired result" , "productive" .)