Pleased with simplicity (4)
I believe the answer is:
ease
'simplicity' is the definition.
(synonyms)
'pleased with' is the wordplay.
'with' says the answer is hidden in the clue.
'EASE' is hidden within '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" .)