Scarlet woman's cabal causing diversion (3,7)
I believe the answer is:
red herring
'diversion' is the definition.
(I know that red herring is a type of diversion)
'scarlet woman's cabal' is the wordplay.
'scarlet' becomes 'red' (synonyms).
'woman's' becomes 'her' (belonging to a woman).
'cabal' becomes 'ring' (I've seen this in another clue).
'red'+'her'+'ring'='RED HERRING'
'causing' acts as a link.
(Other definitions for red herring that I've seen before include "What distracts" , "fish" , "(Fishy) diversion" , "Diversion intended to distract attention from the main issue" , "food?" .)