Fighting with chorus in challenges such as these (8,6)
I believe the answer is:
crossing swords
'fighting' is the definition.
'chorus in challenges such as these' is the wordplay.
'chorus' becomes 'sing' (to chorus is to sing in chorus).
'in' is an insertion indicator.
'challenges such as these' becomes 'crosswords' (challenges such as this crossword).
'sing' placed into 'crosswords' is 'CROSSING SWORDS'.
'with' is the link.
(Other definitions for crossing swords that I've seen before include "in a row - with 23a" , "having a quarrel" .)