Principle involved in first-rate networking (5)
I believe the answer is:
tenet
'principle' is the definition.
(I've seen this before)
'involved in first-rate networking' is the wordplay.
'involved in' indicates the answer is hidden within the clue.
'TENET' can be found hidden inside 'first rate networking'.
(Other definitions for tenet that I've seen before include "A religious doctrine proclaimed as true without proof" , "Article of belief" , "Palindromic principle or belief" , "Matter of belief" , "Item of belief" .)