Ruler requests a refund in part (4)
I believe the answer is:
tsar
'ruler' is the definition.
(historical term for Russian king)
'requests a refund in part' is the wordplay.
'in part' indicates a hidden word.
'TSAR' is hidden within 'requests a refund'.
(Other definitions for tsar that I've seen before include "Ruler finally executed" , "Old Russian ruler" , "Russian ruler (S, not Z)" , "Russian leader" , "Word derived from Caesar, used by European rulers since 1547" .)