Curb transport following jailbirds (9)
I believe the answer is:
constrain
'curb' is the definition.
(thesaurus)
'transport following jailbirds' is the wordplay.
'transport' becomes 'train' (train is a kind of transport).
'following' is a charade indicator (letters next to each other).
'jailbirds' becomes 'cons' (I've seen this in another clue).
'train' put after 'cons' is 'CONSTRAIN'.
(Other definitions for constrain that I've seen before include "Restrict the extent of" , "Compel; constrict" , "Lock up" , "Restrict scope of (an activity)" , "Force" .)