Lust worried an eastern ruler (6)
I believe the answer is:
sultan
'eastern ruler' is the definition.
(title for a royal in some Muslim countries)
'lust worried an' is the wordplay.
'worried' indicates an anagram.
'lust' is an anagram of 'sult'.
'sult'+'an'='SULTAN'
(Other definitions for sultan that I've seen before include "Muslim ruler" , "One governs" , "Ruler of Brunei" , "Chicken" , "Sovereign of a Muslim state" .)