Dog keeping new queen calm (8)
I believe the answer is:
tranquil
'calm' is the definition.
('tranquil' can be a synonym of 'calm')
'dog keeping new queen' is the wordplay.
'dog' becomes 'trail' ('trail' can be a synonym of 'dog'**).
'keeping' is an insertion indicator.
'new' becomes 'n'.
'queen' becomes 'qu'.
'n'+'qu'='nqu'
'trail' placed around 'nqu' is 'TRANQUIL'.
(Other definitions for tranquil that I've seen before include "Calm and undisturbed, at peace" , "Peaceful and quiet, not agitated" , "Serenely quiet or peaceful" , "composed" , "Calm and serene" .)