Trueman not prepared for series of games (10)
I believe the answer is:
tournament
'series of games' is the definition.
(I've seen this before)
'trueman not prepared' is the wordplay.
'prepared' indicates an anagram.
'trueman'+'not'='truemannot'
'truemannot' with letters rearranged gives 'TOURNAMENT'.
'for' is the link.
(Other definitions for tournament that I've seen before include "open perhaps" , "Series of events" , "Jousting competition" , "pageant" , "Sports event" .)