Abandonment when one's tired out
I believe the answer is:
desertion
'abandonment' is the definition.
(synonyms)
'one's tired out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'ones'+'tired'='onestired'
'onestired' anagrammed gives 'DESERTION'.
'when' is the link.
(Other definitions for desertion that I've seen before include "flight" , "going AWOL" , "Abandonment" .)