Muslim ruler old poem recalled (4)
I believe the answer is:
emir
'muslim ruler' is the definition.
(I've seen this in another clue)
'old poem recalled' is the wordplay.
'old poem' becomes 'rime' (archaic spelling of 'rhyme').
'recalled' is a reversal indicator.
'rime' in reverse letter order is 'EMIR'.
(Other definitions for emir that I've seen before include "Eastern title" , "Islamic chieftain" , "Eastern ruler in mire" , "Ruler or chieftain in Arabia" , "Local chief" .)