Joint favourite team (7)

I believe the answer is:

topside

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'joint' is the definition.
(I've seen this before)

'favourite team' is the wordplay.
'favourite' becomes 'top' (I can't justify this - if you can you should believe this answer much more).
'team' becomes 'side' (both can mean a sports team).
'top'+'side'='TOPSIDE'

Can you help me to learn more?

(Other definitions for topside that I've seen before include "Dish" , "Lean cut of beef, no bone" , "Joint" , "Deposit (anag) -- cut of meat" , "Cut of beef from thigh" .)

I've seen this clue in The Guardian.

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