A little red engine in the first garden (4)
I believe the answer is:
eden
'first garden' is the definition.
(I've seen this before)
'a little red engine in' is the wordplay.
'a little' indicates a hidden word (a little bit of the clue).
'EDEN' is hidden in the letters of 'red engine in'.
'the' is the link.
(Other definitions for eden that I've seen before include "The - - Project, Cornwall" , "The best of all gardens" , "The first garden" , "happy state" , "Old Testament garden" .)