Mark wonderful staff (4)
I believe the answer is:
mace
'staff' is the definition.
(a mace is a ceremonial staff or stick)
'mark wonderful' is the wordplay.
'mark' becomes 'm'.
'wonderful' becomes 'ace' (ace can informally mean very good).
'm'+'ace'='MACE'
(Other definitions for mace that I've seen before include "Came to get ceremonial staff" , "Spiked club" , "Medieval weapon or kind of spice" , "Spice; ceremonial baton" , "put on the rack?" .)