Doctor detects rare formula known only to a few (5,6)
I believe the answer is:
trade secret
'formula known only to a few' is the definition.
(secret within a company)
'doctor detects rare' is the wordplay.
'doctor' is an anagram indicator.
'detects'+'rare'='detectsrare'
'detectsrare' with letters rearranged gives 'TRADE SECRET'.
(Other definitions for trade secret that I've seen before include "Information a company holds on to" , "Proprietary information" , "wrinkle?" , "professional knowledge" , "Confidential commercial information" .)