Personal ambition that's a setback for the team (3,4)
I believe the answer is:
own goal
'personal ambition' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for own goal that I've seen before include "Football mishap" , "embarrassing error" , "unintentional problem for herself, say" , "Self-inflicted setback" , "Self-inflicted damage" .)