Subsidiary activity of team left in the capital of Egypt (8)
I believe the answer is:
sideline
'subsidiary activity' is the definition.
(I've seen this before)
'team left in the capital of egypt' is the wordplay.
'team' becomes 'side' (both can mean a sports team).
'left' becomes 'l' (common abbreviation).
'the capital of' suggests taking the first letters.
The initial letter of 'egypt' is 'e'.
'side'+'l'+'in'+'e'='SIDELINE'
'of' is the link.
(Other definitions for sideline that I've seen before include "Activity outside one's main job" , "not my main interest" , "Take out of the picture" , "subsidiary source of income" , "second job" .)