Arab ruler consumed by backward experiment (4)
I believe the answer is:
emir
'arab ruler' is the definition.
(type of ruler in some countries)
'consumed by backward experiment' is the wordplay.
'backward' says the letters should be written in reverse.
'consumed by' says the answer is hidden in the clue (inserted letters get consumed).
'rime' is hidden within 'experiment'.
'rime' in reverse letter order is 'EMIR'.
(Other definitions for emir that I've seen before include "Islamic ruler" , "Islamic chieftain" , "Middle-Eastern ruler" , "Ruler in the Middle East and mire" , "Middle Eastern ruler" .)