Expenses covering ten swimming competitions (8)
I believe the answer is:
contests
'competitions' is the definition.
('contest' can be a synonym of 'competition')
'expenses covering ten swimming' is the wordplay.
'expenses' becomes 'costs' (cost is a kind of expense).
'covering' is an insertion indicator.
'swimming' is an anagram indicator (letters swim around into a new order).
'ten' is an anagram of 'nte'.
'costs' enclosing 'nte' is 'CONTESTS'.
(Other definitions for contests that I've seen before include "sporting events?" , "Matches" , "Struggles between rivals" , "Disputes; competitions" , "Competitions, struggles" .)