Wander aimlessly around eastern part of Thar Desert (6)
I believe the answer is:
maroon
'desert' is the definition.
(to maroon someone is to desert them somewhere)
'wander aimlessly around eastern part of thar' is the wordplay.
'wander aimlessly' becomes 'moon' (to moon about).
'around' is an insertion indicator.
'eastern part of' indicates taking half (the rightmost half).
'thar' halved is 'ar'.
'moon' going around 'ar' is 'MAROON'.
(Other definitions for maroon that I've seen before include "Purplish colour" , "Brownish-crimson - abandon ashore" , "Dark crimson" , "Strand, isolate" , "Reddish-brown" .)