Sneakiness — the last resort? (7)
I believe the answer is:
stealth
'sneakiness' is the definition.
(I've seen this in another clue)
'the last resort?' is the wordplay.
'resort?' indicates anagramming the letters (I've seen 'resorting' mean this).
'the'+'last'='thelast'
'thelast' is an anagram of 'STEALTH'.
(Other definitions for stealth that I've seen before include "Cats display this" , "word to define secrecy" , "Unseen machination" , "Quiet or secret way of behaviour" , "Furtive behaviour" .)