Detectives work out how to cross Swords (8)
I believe the answer is:
disagree
'to cross swords' is the definition.
I can't judge whether this definition defines the answer.
'detectives work out' is the wordplay.
'detectives' becomes 'dis' (Detective Inspectors, DIs).
'work out' becomes 'agree' (I am not sure about this - if you are sure you should believe this answer much more).
'dis'+'agree'='DISAGREE'
'how' acts as a link.
Can you help me to learn more?
(Other definitions for disagree that I've seen before include "Row" , "Express a contrary view" , "Differ, dissent" , "dispute" , "Have conflicting opinions" .)