Competition solicitor adopting unbalanced manner (10)
I believe the answer is:
tournament
'competition' is the definition.
(tournament is a kind of competition)
'solicitor adopting unbalanced manner' is the wordplay.
'solicitor' becomes 'tout' (someone who solicits business).
'adopting' indicates putting letters inside (inserted letters are taken on or adopted).
'unbalanced' is an anagram indicator.
'manner' anagrammed gives 'rnamen'.
'tout' going around 'rnamen' is 'TOURNAMENT'.
(Other definitions for tournament that I've seen before include "open perhaps" , "pageant" , "meeting!" , "Jousting competition" , "military display" .)