Mark has excellent staff (4)
I believe the answer is:
mace
'staff' is the definition.
(a mace is a ceremonial staff or stick)
'mark has excellent' is the wordplay.
'mark' becomes 'm'.
'has' says to put letters next to each other.
'excellent' becomes 'ace' (ace can informally mean very good).
'm'+'ace'='MACE'
(Other definitions for mace that I've seen before include "Spice; ceremonial baton" , "Came to find ceremonial staff" , "Came to get ceremonial staff" , "Came to get ancient weapon" , "Staff - ground nutmeg" .)