The empty trap principle (5)
I believe the answer is:
tenet
'principle' is the definition.
(a tenet is a principle or value)
'the empty trap' is the wordplay.
'empty' means to remove the middle letters.
'trap' becomes 'net' (net is a type of trap).
'the' with its centre taken out is 'te'.
'te'+'net'='TENET'
(Other definitions for tenet that I've seen before include "Canon" , "A belief or credo - it's a palindrome" , "Article of belief" , "Dogma or principle" , "A palindromic doctrine or belief" .)