Intends taking one in the lowlands (6)
I believe the answer is:
plains
'the lowlands' is the definition.
(thesaurus)
'intends taking one' is the wordplay.
'intends' becomes 'plans' (planning is a kind of intending).
'taking' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'plans' enclosing 'i' is 'PLAINS'.
'in' is the link.
(Other definitions for plains that I've seen before include "Extensive tracts of level open land" , "Prairies" , "Large tracts of level open land" , "Flats" , "Grasslands" .)