Concealment the last resort (7)
I believe the answer is:
stealth
'concealment' is the definition.
(stealth is a kind of concealment)
'the last resort' is the wordplay.
'resort' indicates anagramming the letters.
'the'+'last'='thelast'
'thelast' with letters rearranged gives 'STEALTH'.
(Other definitions for stealth that I've seen before include "Avoidance of detection by moving carefully" , "Cautious and surreptitious action or movement" , "underhand dealing" , "Cats display this" , "Avoiding detection by moving carefully" .)