Team sport organised alongside river, generally (3,3,4,4)
I believe the answer is:
for the most part
'generally' is the definition.
(thesaurus)
'team sport organised alongside river' is the wordplay.
'organised' is an anagram indicator.
'alongside' means one lot of letters go next to another.
'river' becomes 'forth' (Scottish river).
'team'+'sport'='teamsport'
'teamsport' anagrammed gives 'emostpart'.
'emostpart' after 'forth' is 'FOR THE MOST PART'.
(Other definitions for for the most part that I've seen before include "Usually" , "in general" , "Mainly" , "Chiefly" .)