Arrest invalidly, ignoring the odds (4)

I believe the answer is:

nail

'arrest' is the definition.
(I know that arrest can be written as nail)

'invalidly ignoring the odds' is the wordplay.
'ignoring the odds' indicates alternate letters (letters in odd-numbered positions are removed).
The alternating letters of 'invalidly' are 'NAIL'.

(Other definitions for nail that I've seen before include "thing for keeping things together" , "Hammer's target" , "one under the hammer" , "Hammered individual" , "SECOND PART OF 17" .)

I've seen this clue in The Independent.

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