Tedious business plan oddly supported by a tennis champ (7)
I believe the answer is:
palaver
'tedious business' is the definition.
'palaver' can be an answer for 'business' (thesaurus). I'm not sure about the 'tedious' bit.
'plan oddly supported by a tennis champ' is the wordplay.
'oddly' means one should take alternating letters (letters in the odd-numbered positions are used).
'supported by' says to put letters next to each other (in a down clue, some letters hold up others).
'a tennis champ' becomes 'laver' (I've seen this in another clue).
The alternate letters of 'plan' are 'pa'.
'pa'+'laver'='PALAVER'
Can you help me to learn more?
(Other definitions for palaver that I've seen before include "Confused talk and activity" , "Hubbub; lengthy fuss" , "Fuss and bother" , "tedious bureaucracy" , "Kind of discussion or idle chatter" .)