Release the French racecourse spy (3,3)
I believe the answer is:
let out
'release' is the definition.
(I know that let out is a type of release)
'the french racecourse spy' is the wordplay.
'the french' becomes 'le' ('the' in French).
'racecourse spy' becomes 'tout' (gambler who scouts out a race course).
'le'+'tout'='LET-OUT'
(Other definitions for let out that I've seen before include "Release or blab secret" , "released from prison" , "Leak" , "Release from confinement or loosen garment" , "Allow to go free" .)