Minor surgery ultimately prohibited by hospital (5)
I believe the answer is:
youth
'minor' is the definition.
(thesaurus)
'surgery ultimately prohibited by hospital' is the wordplay.
'ultimately' says to take the final letters.
'prohibited' becomes 'out' (synonyms).
'by' says to put letters next to each other.
'hospital' becomes 'H' (abbreviation for hospital on maps).
The final letter of 'surgery' is 'y'.
'y'+'out'+'h'='YOUTH'
(Other definitions for youth that I've seen before include "Immaturity" , "Salad days" , "Early part of life" , "next generation" , "Children" .)