Moving all to Hay? A religious leader? (9)
I believe the answer is:
ayatollah
'religious leader?' is the definition.
(I've seen this before)
'moving all to hay? a' is the wordplay.
'moving' indicates an anagram.
'all'+'to'+'hay'+'a'='alltohaya'
'alltohaya' with letters rearranged gives 'AYATOLLAH'.
(Other definitions for ayatollah that I've seen before include "religious authority" , "High-ranking Shiite religious leader" , "Iranian leader" , "Senior Iranian cleric" , "Shiite leader, possibly in 10 across" .)