Touch down on eastern half of this detached territory (6)
I believe the answer is:
island
'this detached territory' is the definition.
(I've seen this before)
'touch down on eastern half' is the wordplay.
'touch down' becomes 'land' (eg touch down in a plane).
'on' is a charade indicator (letters next to each other).
'eastern' becomes 'ibis' (I've seen this before).
'half' means to take half the letters.
'ibis' with half the letters taken is 'is'.
'land' after 'is' is 'ISLAND'.
'of' acts as a link.
(Other definitions for island that I've seen before include "Area in the main" , "Boffin, Baffin or Bali, say" , "Eg, eyot or inch" , "See 12" , "6 Across, for example" .)