Excel, almost certain to involve a teammate (7)
I believe the answer is:
surpass
'excel' is the definition.
(I know that excel can be written as surpass)
'almost certain to involve a teammate' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'certain' becomes 'sure' (synonyms).
'to involve a teammate' becomes 'pass' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sure' with its last letter taken off is 'sur'.
'sur'+'pass'='SURPASS'
Can you help me to learn more?
(Other definitions for surpass that I've seen before include "Be better than (another)" , "Excel" , "eclipse visible" , "Outdo" , "Exceed" .)