On hand (9)
(Other definitions for operative that I've seen before include "Worker in manufacturing" , "Significant" , "Having force - skilled worker" , "Machinist - working" , "Functioning; worker" .)
'on hand' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for available that I've seen before include "Able to be used, free" , "To hand" , "Can be had or obtained, in stock" , "Accessible and ready for use" , "Obtainable or accessible" .)