Close studies on the East (5)
I believe the answer is:
dense
'close' is the definition.
(thesaurus)
'studies on the east' is the wordplay.
'studies' becomes 'dens' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'the east' becomes 'e' (synonyms).
'dens'+'e'='DENSE'
(Other definitions for dense that I've seen before include "Close-packed" , "Closely packed" , "Tightly packed - stupid" , "Thick and tightly-packed" , "Stupid; compacted" .)