Illuminates thin head moving east (6)
I believe the answer is:
lights
'illuminates' is the definition.
('light' can be a synonym of 'illuminate')
'thin head moving east' is the wordplay.
'thin' becomes 'light' (similar in meaning).
'head moving east' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'light'+'s'='LIGHTS'
(Other definitions for lights that I've seen before include "Comes down" , "See 11" , "Fairy _;" , "SECOND PART OF 13" , "Understanding" .)