Calm at opening position (7)
I believe the answer is:
placate
'calm' is the definition.
(placating is a kind of calming)
'at opening position' is the wordplay.
'opening' indicates putting letters inside (some letters open a gap in others).
'position' becomes 'place' (synonyms).
'at' inserted into 'place' is 'PLACATE'.
(Other definitions for placate that I've seen before include "Pale cat could pacify" , "Make calm, conciliate" , "Mollify, soothe anger" , "Calm, pacify, appease" , "Make less angry" .)