Critical point during surgery - essentially resting on anaesthetist's complex calculations (6-9)
I believe the answer is:
number-crunching
'complex calculations' is the definition.
(I've seen this before)
'critical point during surgery essentially resting on anaesthetist's' is the wordplay.
I cannot quite see how this works, but
'point' could be 'n' (North) and 'n' is found in the answer.
'during' could be 'in' (e.g. during February means in February) and 'in' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for number-crunching that I've seen before include "Making lots of calculations" , "Performing large numbers of calculations" .)