Come in from barren terrain (5)
I believe the answer is:
enter
'come in' is the definition.
(synonyms)
'from barren terrain' is the wordplay.
'from' says the answer is hidden in the clue.
'ENTER' is hidden in the letters of 'barren terrain'.
(Other definitions for enter that I've seen before include "Infiltrate" , "Gain admission" , "Come/go in" , "Record (in a log)" , "Pierce" .)