Nothing keeping article secure (4)
I believe the answer is:
nail
'secure' is the definition.
(both can mean to apprehend or capture)
'nothing keeping article' is the wordplay.
'nothing' becomes 'nil' (eg nil is zero in football).
'keeping' means one lot of letters goes inside another (some letters kept inside).
'article' becomes 'a' (the indefinite article in English).
'nil' going around 'a' is 'NAIL'.
(Other definitions for nail that I've seen before include "Fasten - detect and expose" , "Fixing spike" , "Hammer's target" , "Carpentry fastener" , "Horny part of the digit" .)