Trail the convict (3)
I believe the answer is:
lag
I believe this clue is a double definition.
'trail' is the first definition.
(both can mean to go behind)
'the convict' is the second definition.
(thesaurus)
(Other definitions for lag that I've seen before include "Dawdle" , "habitual criminal?" , "Drop behind" , "trail" , "Fall behind on march" .)