Gained an advantage, being committed to staff (6)
I believe the answer is:
scored
I believe this is a double definition.
'gained an advantage' is the first definition.
'committed to staff' is the second definition.
(as in committing musical notes to a staff or stave)
'being' acts as a link.
(Other definitions for scored that I've seen before include "Kept count" , "Got a goal" , "graded" , "Made runs" , "Put ball in net - made deep groove" .)