Married spy advanced in shade (7)
I believe the answer is:
magenta
'shade' is the definition.
(I've seen this before)
'married spy advanced' is the wordplay.
'married' becomes 'm'.
'spy' becomes 'agent' (I've seen this before**).
'advanced' becomes 'a'.
'm'+'agent'+'a'='MAGENTA'
'in' is the link.
(Other definitions for magenta that I've seen before include "this might be an ink" , "Bright purplish red or magnate" , "Light purplish-red" , "Purplish-red - battle" , "Reddish purple" .)