Some thief, if threatened - may invoke this? (5)
I believe the answer is:
fifth
'invoke this?' is the definition.
The definition suggests a singular noun which matches the answer.
'some thief if threatened' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'FIFTH' can be found hidden inside 'thief if threatened'.
'may' acts as a link.
Can you help me to learn more?
(Other definitions for fifth that I've seen before include "US amendment guaranteeing the right to silence" , "Musical interval" , "Twenty percent" , "- Column is a group working for the enemy" , "Fraction" .)