Curvaceous mimic, learner in cast (7)
I believe the answer is:
shapely
'curvaceous' is the definition.
(I've seen this before)
'mimic learner in cast' is the wordplay.
'mimic' becomes 'ape' (I've seen this before).
'learner' becomes 'l'.
'in' indicates putting letters inside.
'cast' becomes 'shy' (I've seen this before**).
'ape'+'l'='apel'
'apel' going into 'shy' is 'SHAPELY'.
(Other definitions for shapely that I've seen before include "Pleasingly formed" , "Looking good?" , "Curvaceous" , "Attractively proportioned" , "Well-turned" .)