Excellent anaesthetic for two or three? (5,6)
I believe the answer is:
prime number
'two or three?' is the definition.
I can't judge whether this defines the answer.
'excellent anaesthetic' is the wordplay.
'excellent' becomes 'prime'.
'anaesthetic' becomes 'number' (i.e. something that makes things numb).
'prime'+'number'='PRIME NUMBER'
'for' is the link.
Can you help me to learn more?
(Other definitions for prime number that I've seen before include "2011, say" , "One with no divisors" , "One providing amusement" , "Two or three perhaps" , "2 or 3 -- but not 4" .)