Train to be articulate (7)
I believe the answer is:
express
This clue is a double definition.
'train' is the first definition.
(I've seen this before)
'be articulate' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for express that I've seen before include "Fast train; specific" , "Say; fast train" , "Verbalise - very fast" , "Quickly" , "Non-stop(ping)" .)