Pleased with simplicity (4)
I believe the answer is:
ease
'simplicity' is the definition.
(synonyms)
'pleased with' is the wordplay.
'with' indicates a hidden word.
'EASE' is hidden in the letters of 'pleased'.
(Other definitions for ease that I've seen before include "Poise or leisure" , "Freedom from discomfort or anxiety" , "Comfort or freedom from difficulty" , "Comfort; simplicity" , "Facilitate; repose" .)