Where head nurse is progressing (6)
I believe the answer is:
onward
'is progressing' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for onward that I've seen before include "Advancing (like Christian soldiers?)" , "In a forward direction" , "In front" , "Advance, Christian soldiers, marching as to war" , "With advancing motion" .)