Cunning is the heartless entertainer (7)
I believe the answer is:
artiste
'entertainer' is the definition.
(artiste is a kind of entertainer)
'cunning is the heartless' is the wordplay.
'cunning' becomes 'art' (I've seen this before).
'heartless' means to remove the middle letters.
'the' with its centre taken out is 'te'.
'art'+'is'+'te'='ARTISTE'
(Other definitions for artiste that I've seen before include "One entertaining" , "'Public performer, dancer or singer (7)'" , "Attires like entertainer" , "Performers" , "Professional performer" .)