Inwardly composed, at ease, calm (6)
I believe the answer is:
sedate
'calm' is the definition.
(I know that calm can be written as sedate)
'inwardly composed at ease' is the wordplay.
'inwardly' says the answer is hidden in the clue (I've seen this in other clues).
'SEDATE' is hidden within 'composed at ease'.
(Other definitions for sedate that I've seen before include "Unexciting" , "grave" , "Calm and dignified in manner" , "Give tranquilliser to" , "Slow" .)