Came up behind nurses beginning to operate (5)
I believe the answer is:
arose
'came up' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for arose that I've seen before include "Became apparent" , "Emerged from" , "Happened" , "Issued" , "Sprang up" .)