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The
spies’
line
of
argument
(6)
The spies’ line of argument (6)
hints
0
checks
0
hints
The definition is at the end of the clue.
How the clue works
Look at line of argument — that's your definition. For the wordplay, it's a charade: THE sits right there in the clue as is, then spies points you to SIS, the Secret Intelligence Service, and the two pieces together give you your answer.