Opposing element in camp, trendy about nothing in argument (10)
I believe the answer is:
contention
'argument' is the definition.
(I know that argument can be written as contention)
'opposing element in camp trendy about nothing' is the wordplay.
'opposing' becomes 'con' (I've seen this in another clue).
'element in camp' becomes 'tent' (a camp includes tents).
'trendy' becomes 'in' ('in' can mean fashionable).
'about' is an insertion indicator.
'nothing' becomes 'o' (looks like zero - 0).
'in' enclosing 'o' is 'ion'.
'con'+'tent'+'ion'='CONTENTION'
'in' is the link.
(Other definitions for contention that I've seen before include "heated argument" , "Judgment" .)