Lauder confused about mathematical fundamental in anaesthetic injection (8)
I believe the answer is:
epidural
'fundamental in anaesthetic injection' is the definition.
The definition suggests a singular noun which matches the answer.
'lauder confused about mathematical' is the wordplay.
'confused' is an anagram indicator.
'about' means one lot of letters goes inside another.
'mathematical' becomes 'pi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lauder' with letters rearranged gives 'edural'.
'edural' enclosing 'pi' is 'EPIDURAL'.
Can you help me to learn more?
(Other definitions for epidural that I've seen before include "Injection of anaesthetic into the spinal cord" , "Anaesthetic used in childbirth" , "Anaesthetic injected into the spinal cord" , "Painkiller" .)