Team rows without cox, finally fixing thing at sea (10)
I believe the answer is:
'team rows' is the definition.
The definition suggests a singular noun which matches the answer.
'without cox finally fixing thing at sea' is the wordplay.
'without cox' becomes 'infi' (I am not sure about this - if you are sure you should believe this answer much more).
'finally' says to take the final letters.
'at sea' is an anagram indicator.
The last letter of 'fixing' is 'g'.
'thing' is an anagram of 'hting'.
Can you help me to learn more?
(Another definition for infighting that I've seen is " Conflict within a group".)