Half a minute or lower (5)
I believe the answer is:
minor
'lower' is the definition.
(thesaurus)
'half a minute or' is the wordplay.
'half a' indicates taking half.
'minute' halved is 'min'.
'min'+'or'='MINOR'
(Other definitions for minor that I've seen before include "Person not yet of legal age" , "Under-age or of little importance" , "Of little significance" , "Less important" , "Small-scale - child" .)