Couch in train (7)
I believe the answer is:
express
I believe this clue is a double definition.
'couch' is the first definition.
(thesaurus)
'train' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for express that I've seen before include "Explicit" , "set forth" , "Verbalise - train" , "Of train, travelling rapidly with few or no stops" , "Squeeze out - quick" .)